Remove the Git monkeypatches

[mpapis]

for Config class to work correctly we had to patch the Git tickets are:

• Allow creating new config entries ruby-git/ruby-git#398
• Fix Git module config method ruby-git/ruby-git#399
• Refactor git config ruby-git/ruby-git#400

after those tickets get merged we can cleanup our patches

[mpapis]

rebased the PR's and asked for next steps

[dennissivia]

@mpapis Is there any progress in accepting the upstream PRs?

[mpapis]

Unfortunately looks like there there is no maintainer, few other people patches got accepted, but bulk of PRs is waiting for review including ours