Update issue.go with labels documentation (labels content, not ids) (go-gitea#35522)

For go-gitea#35521

---------

Signed-off-by: Fabien Benetou <[email protected]>

Author: Utopiah

routers/api/v1/repo/issue.go

@@ -351,7 +351,7 @@ func ListIssues(ctx *context.APIContext) {
 	//   enum: [closed, open, all]
 	// - name: labels
 	//   in: query
-	//   description: comma separated list of labels. Fetch only issues that have any of this labels. Non existent labels are discarded
+	//   description: comma separated list of label names. Fetch only issues that have any of this label names. Non existent labels are discarded.
 	//   type: string
 	// - name: q
 	//   in: query