Fix DatabaseCleaner error when running RSpec

[ribose-jeffreylau]

As reported in #109 (comment)

[codecov]

Codecov Report

Merging #110 (56a846a) into master (2391ea7) will decrease coverage by 0.25%.
The diff coverage is 87.50%.

@@            Coverage Diff             @@
##           master     #110      +/-   ##
==========================================
- Coverage   99.46%   99.20%   -0.26%     
==========================================
  Files          24       24              
  Lines         371      376       +5     
==========================================
+ Hits          369      373       +4     
- Misses          2        3       +1     

Impacted Files	Coverage Δ
spec/support/db_cleaner.rb	94.44% <87.50%> (-5.56%)	⬇️

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[ribose-jeffreylau]

This PR includes some modifications suggested in #107 (and in the links buried within), which seem to have solved the bundler version issues. @skalee maybe you'd want to include the changes in https://github.com/riboseinc/attr_masker/tree/use-best-bundler-in-gha first, then I can rebase these commits on them?

[skalee]

Thanks! I'll take a look. A few more maintenance updates are needed in this gem so I'll take care about them too.

[ribose-jeffreylau]

Closing in favour of #116