chore: Report warning on .github/workflows/ci.yaml (#742)

* fix: Report warning on `.github/workflows/ci.yaml`

Not all files in `.github/workflows` are managed, only `ci.yaml`.

Related false-positive: googleapis/repo-automation-bots#1952 (comment)

* fix: Report warning on `.github/workflows/ci.yaml`

Not all files in `.github/workflows` are managed, only `ci.yaml`.
Source-Link: googleapis/synthtool@2430f8d
Post-Processor: gcr.io/repo-automation-bots/owlbot-nodejs:latest@sha256:14aaee566d6fc07716bb92da416195156e47a4777e7d1cd2bb3e28c46fe30fe2

.github/.OwlBot.lock.yaml

@@ -1,4 +1,3 @@
 docker:
-  digest: sha256:f556e6e7be625deb1b2429fe608df27be57185c3e6b7d39ee0059f1609f17530
-  image: gcr.io/repo-automation-bots/owlbot-nodejs:latest  
-
+  image: gcr.io/repo-automation-bots/owlbot-nodejs:latest
+  digest: sha256:14aaee566d6fc07716bb92da416195156e47a4777e7d1cd2bb3e28c46fe30fe2

.github/generated-files-bot.yml

@@ -3,8 +3,8 @@ generatedFiles:
   message: '`.kokoro` files are templated and should be updated in [`synthtool`](https://github.com/googleapis/synthtool)'
 - path: '.github/CODEOWNERS'
   message: 'CODEOWNERS should instead be modified via the `codeowner_team` property in .repo-metadata.json'
-- path: '.github/workflows/**'
-  message: '`.github/workflows` (GitHub Actions) should be updated in [`synthtool`](https://github.com/googleapis/synthtool)'
+- path: '.github/workflows/ci.yaml'
+  message: '`.github/workflows/ci.yaml` (GitHub Actions) should be updated in [`synthtool`](https://github.com/googleapis/synthtool)'
 - path: '.github/generated-files-bot.+(yml|yaml)'
   message: '`.github/generated-files-bot.(yml|yaml)` should be updated in [`synthtool`](https://github.com/googleapis/synthtool)'
 - path: 'README.md'