[ci] Use github action to approve API docs (#187246)

Cleans up our auto-approve scripts a bit to be consistent. This matches
the auto-approve backport workflow.

.buildkite/scripts/common/setup_job_env.sh

@@ -16,9 +16,6 @@ fi
   GITHUB_TOKEN=$(vault_get kibanamachine github_token)
   export GITHUB_TOKEN
 
-  KIBANA_CI_GITHUB_TOKEN=$(vault_get kibana-ci-github github_token)
-  export KIBANA_CI_GITHUB_TOKEN
-
   KIBANA_DOCKER_USERNAME="$(vault_get container-registry username)"
   KIBANA_DOCKER_PASSWORD="$(vault_get container-registry password)"
   if (command -v docker && docker version) &> /dev/null; then

.buildkite/scripts/steps/api_docs/publish_api_docs.sh

@@ -29,5 +29,3 @@ git push origin "$branch"
 prUrl=$(gh pr create --repo elastic/kibana --base main --head "$branch" --title "[api-docs] $(date +%F) Daily api_docs build" --body "Generated by $BUILDKITE_BUILD_URL" --label "release_note:skip" --label "docs")
 echo "Opened PR: $prUrl"
 gh pr merge --repo elastic/kibana --auto --squash "$prUrl"
-
-GH_TOKEN="$KIBANA_CI_GITHUB_TOKEN" gh pr review --repo elastic/kibana --approve -b "Automated review from $BUILDKITE_BUILD_URL" "$prUrl"

.github/workflows/auto-approve-api-docs.yml

@@ -0,0 +1,18 @@
+on:
+  pull_request:
+    branches:
+      - main
+    types:
+      - opened
+
+jobs:
+  approve:
+    name: Auto-approve API docs
+    runs-on: ubuntu-latest
+    if: |
+      startsWith(github.event.pull_request.head.ref, 'api_docs') &&
+      github.event.pull_request.user.login == 'kibanamachine'
+    permissions:
+      pull-requests: write
+    steps:
+      - uses: hmarr/auto-approve-action@f0939ea97e9205ef24d872e76833fa908a770363 #4.0.0

.github/workflows/auto-approve-backports.yml

@@ -1,7 +1,9 @@
 on:
-  pull_request_target:
+  pull_request:
     branches-ignore:
       - main
+    types:
+      - opened
 
 jobs:
   approve:
@@ -13,4 +15,4 @@ jobs:
     permissions:
       pull-requests: write
     steps:
-      - uses: hmarr/auto-approve-action@v3
+      - uses: hmarr/auto-approve-action@f0939ea97e9205ef24d872e76833fa908a770363 #4.0.0