Use default locale for all mailer actions

[Hemang360]

Fixes #6316
deliver_later serializes I18n.locale at enqueue time. So when a german speaking user confirms gem ownership, all owners get their notification in german instead of english. This PR adds an around_action in ApplicationMailer to force default locale for all mailers.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.51%. Comparing base (23f0be6) to head (f3e0f41).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6425      +/-   ##
==========================================
- Coverage   97.07%   94.51%   -2.56%     
==========================================
  Files         494      494              
  Lines       10514    10577      +63     
==========================================
- Hits        10206     9997     -209     
- Misses        308      580     +272     

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