fix: skip HMR websocket path when forwarding upgrades to user-defined proxies

[bjohansebas]

…

Summary

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Use of AI

[bjohansebas]

ref: #4316

[codecov]

Codecov Report

❌ Patch coverage is 43.47826% with 13 lines in your changes missing coverage. Please review.
✅ Project coverage is 81.52%. Comparing base (28ecc85) to head (3cad324).

Files with missing lines	Patch %	Lines
lib/Server.js	43.47%	13 Missing ⚠️

❗ There is a different number of reports uploaded between BASE (28ecc85) and HEAD (3cad324). Click for more details.

HEAD has 38 uploads less than BASE

Flag	BASE (28ecc85)	HEAD (3cad324)
	41	3

Additional details and impacted files

@@            Coverage Diff             @@
##             next    #5677      +/-   ##
==========================================
- Coverage   88.85%   81.52%   -7.33%     
==========================================
  Files          13       11       -2     
  Lines        5893     4904     -989     
==========================================
- Hits         5236     3998    -1238     
- Misses        657      906     +249     

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