Repository.ListByOrg: Add nebula-preview to receive visibility field

[marcelocarlos]

What type of PR is this?

feature

What this PR does / why we need it:

In addition to the changes added in #1780, this change also ensures the Visibility field is included when calling Repositories.ListByOrg.

Special notes for your reviewer:

None

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[marcelocarlos]

@googlebot I signed it!

[codecov]

Codecov Report

Merging #1795 (22cb4f1) into master (24b281b) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #1795   +/-   ##
=======================================
  Coverage   97.54%   97.54%           
=======================================
  Files          98       98           
  Lines        6383     6383           
=======================================
  Hits         6226     6226           
  Misses         85       85           
  Partials       72       72           

Impacted Files	Coverage Δ
github/repos.go	98.70% <100.00%> (ø)

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[gmlewis]

Thank you, @marcelocarlos !
LGTM.
Merging.