ci: use check-success instead of status-success for GitHub Actions (#35188)

### Reason for this change

After removing the CodeBuild requirement from Mergify in #35174,
automatic PR merging stopped working. Mergify was looking for
status-success=validate-pr and status-success=build, but GitHub Actions
creates check runs, not statuses. CodeBuild used the GitHub Status API,
while GitHub Actions uses the GitHub Checks API.

### Description of changes

Changed all Mergify conditions from status-success=validate-pr and
status-success=build to check-success=validate-pr and
check-success=build to match what GitHub Actions actually creates.

The previous configuration worked because Mergify was only waiting for
the CodeBuild status (which was correctly configured), while the GitHub
Actions conditions were silently failing but not blocking merges.

### Describe any new or updated permissions being added

NA


### Description of how you validated changes

Analyzed GitHub API responses for recent PRs to confirm:
• CodeBuild creates statuses via GitHub Status API
• GitHub Actions creates check runs via GitHub Checks API
• Verified that approved PRs have successful validate-pr and build check
runs but no corresponding statuses

### Checklist
- [x] My code adheres to the [CONTRIBUTING
GUIDE](https://github.com/aws/aws-cdk/blob/main/CONTRIBUTING.md) and
[DESIGN
GUIDELINES](https://github.com/aws/aws-cdk/blob/main/docs/DESIGN_GUIDELINES.md)

----

*By submitting this pull request, I confirm that my contribution is made
under the terms of the Apache-2.0 license*

Author: alvazjor

.mergify.yml

@@ -17,8 +17,8 @@ queue_rules:
       - -approved-reviews-by~=author
       # This is important! It makes the PR Linter work.
       - "#changes-requested-reviews-by=0"
-      - status-success=validate-pr
-      - status-success=build
+      - check-success=validate-pr
+      - check-success=build
     commit_message_template: |-
       {{ title }} (#{{ number }})
       {{ body }}
@@ -37,8 +37,8 @@ queue_rules:
       - -approved-reviews-by~=author
       # This is important! It makes the PR Linter work.
       - "#changes-requested-reviews-by=0"
-      - status-success=validate-pr
-      - status-success=build
+      - check-success=validate-pr
+      - check-success=build
     commit_message_template: |-
       {{ title }} (#{{ number }})
       {{ body }}
@@ -56,8 +56,8 @@ queue_rules:
       - -approved-reviews-by~=author
       # This is important! It makes the PR Linter work.
       - "#changes-requested-reviews-by=0"
-      - status-success=validate-pr
-      - status-success=build
+      - check-success=validate-pr
+      - check-success=build
     commit_message_template: |-
       {{ title }} (#{{ number }})
       {{ body }}
@@ -88,8 +88,8 @@ pull_request_rules:
       - -approved-reviews-by~=author
       # This is important! It makes the PR Linter work.
       - "#changes-requested-reviews-by=0"
-      - status-success=validate-pr
-      - status-success=build
+      - check-success=validate-pr
+      - check-success=build
   - name: automatic priority merge
     actions:
       comment:
@@ -109,8 +109,8 @@ pull_request_rules:
       - -approved-reviews-by~=author
       # This is important! It makes the PR Linter work.
       - "#changes-requested-reviews-by=0"
-      - status-success=validate-pr
-      - status-success=build
+      - check-success=validate-pr
+      - check-success=build
   - name: automatic merge (2+ approvers)
     actions:
       comment:
@@ -130,8 +130,8 @@ pull_request_rules:
       - -approved-reviews-by~=author
       # This is important! It makes the PR Linter work.
       - "#changes-requested-reviews-by=0"
-      - status-success=validate-pr
-      - status-success=build
+      - check-success=validate-pr
+      - check-success=build
   - name: automatic merge (no-squash)
     actions:
       comment:
@@ -151,8 +151,8 @@ pull_request_rules:
       - -approved-reviews-by~=author
       # This is important! It makes the PR Linter work.
       - "#changes-requested-reviews-by=0"
-      - status-success=validate-pr
-      - status-success=build
+      - check-success=validate-pr
+      - check-success=build
   - name: remove stale reviews
     actions:
       dismiss_reviews:
@@ -191,8 +191,8 @@ pull_request_rules:
       - "#approved-reviews-by>=1"
       # This is important! It makes the PR Linter work.
       - "#changes-requested-reviews-by=0"
-      - status-success=validate-pr
-      - status-success=build
+      - check-success=validate-pr
+      - check-success=build
 priority_rules:
   - name: priority for queue `default-merge`
     conditions: