Simplify validation code for listener protocol

[jjngx]

Proposed changes

This PR simplifies validation code for listener protocol.

Checklist

Before creating a PR, run through this checklist and mark each as complete.

• I have read the CONTRIBUTING doc
• I have added tests that prove my fix is effective or that my feature works
• I have checked that all unit tests pass after adding my changes
• [] I have updated necessary documentation
• I have rebased my branch onto main
• I will ensure my PR is targeting the main branch and pulling from my branch from my own fork

[codecov]

Codecov Report

Merging #3885 (b08a146) into main (adba092) will decrease coverage by 0.04%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #3885      +/-   ##
==========================================
- Coverage   51.95%   51.91%   -0.04%     
==========================================
  Files          59       59              
  Lines       16759    16755       -4     
==========================================
- Hits         8707     8699       -8     
- Misses       7756     7758       +2     
- Partials      296      298       +2     

Impacted Files	Coverage Δ
...g/apis/configuration/validation/transportserver.go	96.31% <100.00%> (-0.06%)	⬇️

... and 1 file with indirect coverage changes

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