graphqlbackend: Fix boundary bug in repositoryConnectionResolver

Created by: tsenart

Fixes #4426

Created by: codecov[bot]

Codecov Report

Merging #4427 into master will not change coverage. The diff coverage is 100%.

@@           Coverage Diff           @@
##           master    #4427   +/-   ##
=======================================
  Coverage   47.09%   47.09%           
=======================================
  Files         714      714           
  Lines       43182    43182           
  Branches     1741     1741           
=======================================
  Hits        20335    20335           
  Misses      20939    20939           
  Partials     1908     1908

Impacted Files	Coverage Δ
cmd/frontend/graphqlbackend/repositories.go	30.5% <100%> (ø)

Created by: keegancsmith

Cherry-picked onto 3.4 as b3d1d180495d3313038ee1cae82d553aeeb66604 will add a changelog entry for 3.4.4