ci: Serialize verify-api and format-code per PR

Both workflows auto-commit and push to the PR branch. If both fire on
the same PR and both find changes, the second git push is rejected as
non-fast-forward. Share a concurrency group so only one runs at a time
per PR.

Author: jamescrosswell

.github/workflows/format-code.yml

@@ -7,6 +7,12 @@ on:
       - 'samples/**'
       - '.github/workflows/format-code.yml'
 
+# Serialize with verify-api.yml so the two auto-commit workflows can't race
+# each other's git push on the same PR branch.
+concurrency:
+  group: pr-auto-commit-${{ github.event.pull_request.number }}
+  cancel-in-progress: false
+
 jobs:
   format-code:
     name: Format Code

.github/workflows/verify-api.yml

@@ -7,6 +7,12 @@ on:
       - 'test/Sentry.Testing/ApiExtensions.cs'
       - '.github/workflows/verify-api.yml'
 
+# Serialize with format-code.yml so the two auto-commit workflows can't race
+# each other's git push on the same PR branch.
+concurrency:
+  group: pr-auto-commit-${{ github.event.pull_request.number }}
+  cancel-in-progress: false
+
 jobs:
   run-api-tests:
     name: Run API Approval Tests (${{ matrix.rid }})