tablet: remove max-waiters setting

[vmg]

Description

The new Connection Pool implementation in #14034 no longer allows configuring the maximum amount of waiters in the pool, as it uses uses heuristics (such as maximum wait time) to decide when to start dropping clients under load.

We forgot to remove the flag from the list of CLI flags, however. This PR marks them as deprecated so they can be removed in a future release.

Related Issue(s)

• Fixes Bug Report: queryserver-config-*-pool-waiter-cap flags have no effect in v19 #15234

Checklist

• "Backport to:" labels have been added if this change should be back-ported to release branches
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• Tests were added or are not required
• Did the new or modified tests pass consistently locally and on CI?
• Documentation was added or is not required

Deployment Notes

[vitess-bot]

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (696fe0e) 67.41% compared to head (3e3a39b) 67.56%.
Report is 39 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #15323      +/-   ##
==========================================
+ Coverage   67.41%   67.56%   +0.14%     
==========================================
  Files        1560     1561       +1     
  Lines      192752   193389     +637     
==========================================
+ Hits       129952   130663     +711     
+ Misses      62800    62726      -74     

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