chore(ci): unpin upload-artifact/merge (#1849)

### Briefly, what does this PR introduce?
This PR unpins a github action since with
[v4.4.1](https://github.com/actions/upload-artifact/releases/tag/v4.4.1),
this issue is resolved
(actions/upload-artifact#625).

### What kind of change does this PR introduce?
- [x] Bug fix (issue: technical debt)
- [ ] New feature (issue #__)
- [ ] Documentation update
- [ ] Other: __

### Please check if this PR fulfills the following:
- [ ] Tests for the changes have been added
- [ ] Documentation has been added / updated
- [ ] Changes have been communicated to collaborators

### Does this PR introduce breaking changes? What changes might users
need to make to their code?
No.

### Does this PR change default behavior?
No.

Author: wdconinc

.github/workflows/linux-eic-shell.yml

@@ -1152,9 +1152,7 @@ jobs:
       - get-docs-from-open-prs
     steps:
       - name: Merge GitHub Pages staging artifact
-        # FIXME pinned per https://github.com/actions/upload-artifact/issues/485#issuecomment-2271527517
-        # to avoid https://github.com/eic/EICrecon/actions/runs/10486195490/job/29045183375#step:2:111
-        uses: actions/upload-artifact/[email protected]
+        uses: actions/upload-artifact/merge@v4
         with:
           name: github-pages-staging
           pattern: |