Fix user delete when the user has pushed a gem with an associated API key

[segiddins]

Fixes a report we received via zendesk

[codecov]

Codecov Report

Merging #4130 (eed7358) into master (3cf8bee) will increase coverage by 0.03%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #4130      +/-   ##
==========================================
+ Coverage   98.86%   98.90%   +0.03%     
==========================================
  Files         276      276              
  Lines        6281     6283       +2     
==========================================
+ Hits         6210     6214       +4     
+ Misses         71       69       -2     

Files	Coverage Δ
app/jobs/delete_user_job.rb	100.00% <100.00%> (ø)
app/models/api_key.rb	100.00% <100.00%> (ø)
app/models/gem_info.rb	98.38% <100.00%> (+0.02%)	⬆️

... and 1 file with indirect coverage changes