github/repos: remove omitempty option in BranchRestrictionsRequest

[anGie44]

Closes #1546

Notes:

• this reverts a previous change to the BranchRestrictionsRequest as it does not behave as expected such that restrictions configured for individual repositories still result in an error if users/teams fields are not set e.g.

No subschema in "anyOf" matched.
"teams", "users" weren't supplied.
Not all subschemas of "allOf" matched.
For 'anyOf/1', {"apps"=>["myApp"]} is not a null.

or if set to nil or []string{} e.g.

422 Validation Failed [{Resource: Field: Code: Message:Only organization repositories can have users and team restrictions}]

• in addition, the change introduced a break in behavior for organization-level repositories as discussed in Repositories.UpdateBranchProtection returning 422 Error when restrictions contain empty fields #1546
• a workaround didn't seem feasible as the validation issue seems to be upstream but any further suggestions are greatly appreciated 😃

[codecov]

Codecov Report

Merging #1571 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1571   +/-   ##
=======================================
  Coverage   67.95%   67.95%           
=======================================
  Files          96       96           
  Lines        8762     8762           
=======================================
  Hits         5954     5954           
  Misses       1898     1898           
  Partials      910      910           

Impacted Files	Coverage Δ
github/repos.go	70.04% <ø> (ø)

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[gmlewis]

Thank you, @anGie44 !
LGTM, and unless you know of a solution using curl that we could reverse-engineer, then I don't have any other suggestions than to just go ahead and merge this PR.

Awaiting second LGTM before merging.

[andrew-waters]

LGTM as well

[gmlewis]

Thank you, @andrew-waters!
Merging.

[anGie44]

thank you @gmlewis and @andrew-waters! would love to get this in the next release to help the Terraform Provider Github project benefit from the new features already in v32

[gmlewis]

Sorry for the delay... hopefully I can get to this tomorrow.

[gmlewis]

@anGie44 - this is now available in Release v32.1.0: https://github.com/google/go-github/releases/tag/v32.1.0
Thank you for your patience and understanding!

[anGie44]

Not a problem, @gmlewis! thanks so much for your help and review 😃