Remove duplicated http filters for ExtAuth

[zhaohuabing]

Remove duplicated http filters for Ext Auth.

Part of #2891

[codecov]

Codecov Report

Attention: Patch coverage is 85.29412% with 5 lines in your changes are missing coverage. Please review.

Project coverage is 64.56%. Comparing base (975ef6e) to head (9f8ba6c).
Report is 1 commits behind head on main.

Files	Patch %	Lines
internal/gatewayapi/securitypolicy.go	88.88%	0 Missing and 1 partial ⚠️
internal/xds/translator/basicauth.go	50.00%	0 Missing and 1 partial ⚠️
internal/xds/translator/extauth.go	90.00%	0 Missing and 1 partial ⚠️
internal/xds/translator/oidc.go	66.66%	0 Missing and 1 partial ⚠️
internal/xds/translator/utils.go	90.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2893      +/-   ##
==========================================
+ Coverage   64.52%   64.56%   +0.03%     
==========================================
  Files         122      122              
  Lines       21092    21106      +14     
==========================================
+ Hits        13610    13627      +17     
+ Misses       6634     6632       -2     
+ Partials      848      847       -1     

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[guydc]

LGTM, Thanks!

[arkodg]

LGTM thanks !