tests/util/github: Fix test flakyness

[Turbo87]

gh_id = 0 has a special meaning within our database. Depending on the order of the tests we could sometimes see tests failing because the initial user was created with gh_id = 0. This commit fixes the flakiness by starting the gh_id values at 1 instead.

and yes, I thought I was going insane... 🙈

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.23%. Comparing base (d3d908d) to head (b79f592).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #9980   +/-   ##
=======================================
  Coverage   89.23%   89.23%           
=======================================
  Files         292      292           
  Lines       30409    30409           
=======================================
  Hits        27134    27134           
  Misses       3275     3275           

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