[Website] Deploy workflow always fail for dependabot PRs

[raulcd]

All dependabot PRs fail with:

From https://github.com/apache/arrow-site
 * [new branch]              asf-site   -> deploy/asf-site
 * [new branch]              dependabot/npm_and_yarn/cross-spawn-7.0.6 -> deploy/dependabot/npm_and_yarn/cross-spawn-7.0.6
 * [new branch]              main       -> deploy/main
fatal: 'deploy/gh-pages' is not a commit and a branch 'gh-pages' cannot be created from it
fatal: 'remotes/origin/asf-site' is not a commit and a branch 'gh-pages' cannot be created from it
Error: Process completed with exit code 128.

See the list of closed PRs here:
https://github.com/apache/arrow-site/pulls?q=is%3Apr+label%3Adependencies+is%3Aclosed