Remove bors-ng and switch to GitHub actions merge-queue

.github/workflows/ci.yml

@@ -2,14 +2,12 @@
 
 name: ci
 
-# We want to run CI on all pull requests. Additionally, Bors needs workflows to
-# run on the `staging` and `trying` branches.
+# We want to run CI on all pull requests. Additionally, GitHub actions merge
+# queue needs workflows to run on the `merge_queue` trigger to block merges on
+# them.
 on:
  pull_request:
- push:
- branches:
- - staging
- - trying
+ merge_group:
 
 jobs:
  ci:

.github/workflows/mac-os.yml

@@ -2,8 +2,9 @@
 
 name: ci-mac-os
 
-# We run this workflow during pull request review, but not for Bors merges. We
-# can change this if the workflow is reasonably quick and reliable.
+# We run this workflow during pull request review, but not as a required status
+# for GitHub actions merge-queue merges. We can change this if the workflow is
+# reasonably quick and reliable.
 on: pull_request
 
 jobs:

.github/workflows/size-diff.yml

@@ -3,14 +3,12 @@
 
 name: size-diff
 
-# We want to run this on all pull requests. Additionally, Bors needs workflows
-# to run on the `staging` and `trying` branches to block merges on them.
+# We want to run this on all pull requests. Additionally, GitHub actions merge
+# queue needs workflows to run on the `merge_queue` trigger to block merges on
+# them.
 on:
  pull_request:
- push:
- branches:
- - staging
- - trying
+ merge_group:
 
 jobs:
  size-diff: