Fix mysql2 invalid configuration (#788)

[kossidts]

Please check if the PR fulfills these requirements

• Followed the Contributing guidelines.
• Tests for the changes have been added (for bug fixes/features) with 100% code coverage.
• Docs have been added / updated (for bug fixes / features)

What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)
Exclude configuration options specific to keyv from the mysql2 connection options. This change fixes mysql2 invalid configuration warnings. MySQL2 will likely throw an error in future version.

The change require neither additional tests nor documentation. The tests run with 100% code coverage.

[codecov]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (2e7bcc2) 100.00% compared to head (a6bc47f) 100.00%.

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #789   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           21        21           
  Lines         2419      2419           
  Branches       143       143           
=========================================
  Hits          2419      2419           

Impacted Files	Coverage Δ
packages/mysql/src/index.js	100.00% <100.00%> (ø)

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