Remove CustomMySQLResourceManager

[Polber]

Not needed since https://github.com/apache/beam/pull/29732 was added in Beam 2.56.0

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 41.16%. Comparing base (f14c62c) to head (a21cbc9).

:exclamation: Current head a21cbc9 differs from pull request most recent head 31ff6d1

Please upload reports for the commit 31ff6d1 to get more accurate results.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #1592      +/-   ##
============================================
- Coverage     41.29%   41.16%   -0.13%     
- Complexity     2929     3196     +267     
============================================
  Files           769      764       -5     
  Lines         44602    44448     -154     
  Branches       4770     4760      -10     
============================================
- Hits          18418    18299     -119     
+ Misses        24636    24607      -29     
+ Partials       1548     1542       -6     

Components	Coverage Δ
spanner-templates	61.39% <ø> (-0.01%)	:arrow_down:
spanner-import-export	64.42% <ø> (-0.03%)	:arrow_down:
spanner-live-forward-migration	73.87% <ø> (ø)
spanner-live-reverse-replication	49.70% <ø> (ø)
spanner-bulk-migration	82.06% <ø> (ø)

see 13 files with indirect coverage changes