enhancement: Remove useragent set by RC

[LaurenceJJones]

Fix #3166

Checked all currently supported remediation components (nginx, openresty and traefik) all currently support the new header the upcoming will need to ensure this is set.

/kind enhancement
/area agent

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.

Project coverage is 50.78%. Comparing base (6bd4096) to head (2454bf1).

Files	Patch %	Lines
pkg/appsec/request.go	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3167      +/-   ##
==========================================
- Coverage   50.80%   50.78%   -0.02%     
==========================================
  Files         326      326              
  Lines       38623    38624       +1     
==========================================
- Hits        19621    19614       -7     
- Misses      17078    17083       +5     
- Partials     1924     1927       +3     

Flag	Coverage Δ
bats	40.23% <0.00%> (+0.01%)	⬆️
unit-linux	33.94% <0.00%> (+<0.01%)	⬆️
unit-windows	28.39% <0.00%> (-0.02%)	⬇️

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