BuildDiff: actual list reference to $builds2

Dependencies

• [2] NYIIFA32 BuildDiff: split out from JobsetEval GET impl
• [3] ZAISBSNH BuildDiff: cleanup imports and make slightly more readable
• [4] XJN33EVY BuildDiff: make actual hash ref

Change contents

• replacement in src/lib/Hydra/Helper/BuildDiff.pm at line 44
  [2.838]→[2.838:878](∅→∅)
  − while ($n < scalar($builds2)) {
  [2.838]

  [2.878]
  + while ($n < scalar(@{$builds2})) {