Move dependabot PRs to use GPS #41522
Description
Describe the issue or suggestion
We should use the 1ES-sponsored GitHub Policy Service instead of our own custom action to auto-approve and auto-merge dependabot PRs.
Also, the azure-sdk PRs in dotnet/docs and the dependabot PRs in dotnet/docs-aspire aren't auto-merging (but they are getting labeled as auto-merge). So we need to fix that.