chore: fix failing upgrade-aws-cdk-lib workflow (#1016)

In #1002 we introduced a new workflow to just update `aws-cdk-lib` and
nothing else. Turns out upgrading dependency in subprojects wasn't
really support in projen and that needed a fix first.

This PR fixes the workflow by importing the updated projen dependencies.
The workflow file is renamed to match projen's naming conventions.

---
By submitting this pull request, I confirm that my contribution is made
under the terms of the Apache-2.0 license

Author: mrgrain

.gitattributes

@@ -1235,8 +1235,6 @@ const cli = configureProject(
   }),
 );
 
-// @ts-ignore
-cli.github = repo.github;
 new pj.javascript.UpgradeDependencies(cli, {
   include: ['aws-cdk-lib'],
   semanticCommit: 'feat',