Revert "New/Set-GitHubRepository: Add AllowAutoMerge and UseSquashPrTitleAsDefault Parameters"

[HowardWolosky]

Reverts #358

It turns out that this isn't quite working right.

The use_squash_pr_title_as_default parameter has been deprecated per the documentation in favor of squash_merge_commit_title which works a bit differently.

Additionally, there appears to be a GitHub-side bug at the moment with changing the value of allow_auto_merge (it does not honor the request being sent).

Given this, for the time being we'll revert the change until we know that the feature is working correctly.

/cc: @X-Guardian

[X-Guardian]

I will raise new PRs for these, splitting each one into its own PR. I have just tested my original code for the allow_auto_merge setting on both the new and set cmdlets and it is working fine for me now, so it was probably a transient issue with GitHub when you tested it.