fix: remove redundant --repo flag in preview release cleanup (#6847)

The check_preview_release_workflow.sh script uses exact line matching
(grep -Fxq) to verify the cleanup-preview-releases job contains:

  gh release delete "$preview_tag" --yes

The extra --repo flag is unnecessary in GitHub Actions context since
gh auto-detects the repository from GITHUB_REPOSITORY, and it causes
the Workflow Pin Report check to fail on all PRs.

.github/workflows/build.yml

@@ -1065,7 +1065,7 @@ jobs:
           while IFS= read -r preview_tag; do
             [[ -n "$preview_tag" ]] || continue
             echo "🧹 Deleting preview release $preview_tag (tag kept)"
-            gh release delete "$preview_tag" --repo "${GITHUB_REPOSITORY}" --yes
+            gh release delete "$preview_tag" --yes
             DELETED=$((DELETED + 1))
           done < <(
             jq -r --arg tag "$TAG" '