fix: ignore pseudo-headers

[midgleyc]

HTTP/2 requests made under HttpClient may return pseudo-headers (e.g. ":status", ":version").

When proxying headers from KoL, don't include these headers.

[codecov]

Codecov Report

Merging #667 (91446cb) into main (5582efc) will decrease coverage by 0.00%.
The diff coverage is 0.00%.

@@             Coverage Diff              @@
##               main     #667      +/-   ##
============================================
- Coverage     22.01%   22.01%   -0.01%     
  Complexity     9515     9515              
============================================
  Files          1003     1003              
  Lines        157194   157196       +2     
  Branches      34831    34832       +1     
============================================
  Hits          34614    34614              
- Misses       116305   116307       +2     
  Partials       6275     6275              

Impacted Files	Coverage Δ
...net/sourceforge/kolmafia/request/RelayRequest.java	17.45% <0.00%> (-0.03%)	⬇️

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