fix: remove global.gitAuthor (#11536)

lib/globals.d.ts

lib/platform/azure/index.ts

lib/platform/bitbucket-server/index.spec.ts

lib/platform/bitbucket-server/index.ts

lib/platform/bitbucket/index.spec.ts

lib/platform/bitbucket/index.ts

lib/platform/gitea/index.spec.ts

lib/platform/gitea/index.ts

lib/platform/github/index.spec.ts

lib/platform/github/index.ts

lib/platform/gitlab/__snapshots__/index.spec.ts.snap

lib/platform/gitlab/index.ts

lib/platform/index.ts

lib/util/git/index.spec.ts

lib/util/git/index.ts