Remove error message patterns written in the regular expressions

[azumakuniyuki]

• Regular expressions have been removed from the following classes:
  • Sisimai::Reason::Blocked
  • Sisimai::Reason::MailerError
  • Sisimai::Reason::SpamDetected

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.67%. Comparing base (eab9f30) to head (c0594c9).
Report is 4 commits behind head on 5-stable.

Additional details and impacted files

@@             Coverage Diff              @@
##           5-stable     #543      +/-   ##
============================================
+ Coverage     85.62%   85.67%   +0.04%     
============================================
  Files           135      135              
  Lines          6581     6575       -6     
  Branches       1925     1922       -3     
============================================
- Hits           5635     5633       -2     
  Misses          302      302              
+ Partials        644      640       -4     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.