Add fields to update repository API and create branch protection API to match GitHub APIs

[verbanicm]

No description provided.

[gmlewis]

Thank you, @verbanicm and @sethvargo !
LGTM.
Merging.

[codecov]

Codecov Report

Merging #2709 (2b4ee89) into master (9bfbc00) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #2709   +/-   ##
=======================================
  Coverage   98.05%   98.05%           
=======================================
  Files         131      131           
  Lines       11459    11459           
=======================================
  Hits        11236    11236           
  Misses        152      152           
  Partials       71       71           

Impacted Files	Coverage Δ
github/repos.go	98.84% <ø> (ø)

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[verbanicm]

Thank you @gmlewis !

[verbanicm]

@gmlewis Do you have a set release schedule or can this be cut whenever?

[gmlewis]

@verbanicm - we typically shoot for a release approximately once per month, but we are flexible and can release on demand if there is a pressing need. We are already at 3 weeks since the last release so I can go ahead and prepare a new one.

[verbanicm]

@gmlewis No rush, but you are able, then 🎉

[gmlewis]

@verbanicm - here is the latest release: https://github.com/google/go-github/releases/tag/v50.2.0

[verbanicm]

@gmlewis Awesome, thank you!!