_mysql: db -> database, passwd -> password

[methane]

_mysql uses database and password instead of old db and passwd.
This rename was done in MySQLdb already.

[codecov]

Codecov Report

Merging #513 (6c8573c) into main (16d139c) will not change coverage.
The diff coverage is 50.00%.

@@           Coverage Diff           @@
##             main     #513   +/-   ##
=======================================
  Coverage   85.79%   85.79%           
=======================================
  Files           6        6           
  Lines         542      542           
=======================================
  Hits          465      465           
  Misses         77       77           

Impacted Files	Coverage Δ
MySQLdb/connections.py	87.02% <50.00%> (ø)

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