mysqlctld: Remove unneeded resets in init_db.sql

[dbussink]

This removes the resets for the startup script that we use. These were long ago added for a MariaDB 10.3 workaround which is not supported as a managed tablet anyway anymore.

It also would only needed for an existing node to join a cluster that is otherwise manually emptied. If that's the case, the reset should also be done manually anyway too.

Removing this also ensures we have no logic here that would start failing in the future on MySQL 8.4.0 which removed these statements.

Related Issue(s)

Part of #9515

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 68.41%. Comparing base (2066acc) to head (0abb087).
Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #15832      +/-   ##
==========================================
- Coverage   68.43%   68.41%   -0.03%     
==========================================
  Files        1559     1559              
  Lines      196496   196496              
==========================================
- Hits       134474   134432      -42     
- Misses      62022    62064      +42     

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