release-23.1: ccl/sqlproxyccl: fix possible flake in TestProxyProtocol

[blathers-crl]

Backport 1/1 commits from #105589 on behalf of @jaylim-crl.

/cc @cockroachdb/release

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Fixes #105585.

This commit updates the TestProxyProtocol test to only test the case where RequireProxyProtocol=true. There's no point testing the case where the RequireProxyProtocol field is false since every other tests do not use the proxy protocol (and that case is implicitly covered by them).

It's unclear what is causing this test flake (and it is extremely rare, i.e. 1 legit failure out of 1000 runs [1]). It may be due to some sort of race within the tests, but given that the case is covered by all other tests, this commit opts to remove the test entirely.

[1] https://teamcity.cockroachdb.com/test/-1121006080109385641?currentProjectId=Cockroach_Ci_TestsGcpLinuxX8664BigVm&expandTestHistoryChartSection=true

Release note: None

Release justification: Fixes a test flake.

Epic: none

[blathers-crl]

Thanks for opening a backport.

Please check the backport criteria before merging:

• Patches should only be created for serious issues or test-only changes.
• Patches should not break backwards-compatibility.
• Patches should change as little code as possible.
• Patches should not change on-disk formats or node communication protocols.
• Patches should not add new functionality.
• Patches must not add, edit, or otherwise modify cluster versions; or add version gates.

If some of the basic criteria cannot be satisfied, ensure that the exceptional criteria are satisfied within.

• There is a high priority need for the functionality that cannot wait until the next release and is difficult to address in another way.
• The new functionality is additive-only and only runs for clusters which have specifically “opted in” to it (e.g. by a cluster setting).
• New code is protected by a conditional check that is trivial to verify and ensures that it only runs for opt-in clusters.
• The PM and TL on the team that owns the changed code have signed off that the change obeys the above rules.

Add a brief release justification to the body of your PR to justify this backport.

Some other things to consider:

• What did we do to ensure that a user that doesn’t know & care about this backport, has no idea that it happened?
• Will this work in a cluster of mixed patch versions? Did we test that?
• If a user upgrades a patch version, uses this feature, and then downgrades, what happens?

[cockroach-teamcity]

This change is 

[pjtatlow]

LGTM

[jaylim-crl]

TFTR!