winrt: proxy_resolver should not take into account system config

[sergio-nsk]

If the app sets user proxy.

[codecov]

Codecov Report

Attention: 4 lines in your changes are missing coverage. Please review.

Comparison is base (863f4af) 55.57% compared to head (69b67ff) 57.24%.

Files	Patch %	Lines
resolver_winxp.c	0.00%	2 Missing ⚠️
resolver_gnome3.c	0.00%	1 Missing ⚠️
resolver_posix.c	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #55      +/-   ##
==========================================
+ Coverage   55.57%   57.24%   +1.67%     
==========================================
  Files          53       53              
  Lines        4605     4605              
  Branches     1062     1062              
==========================================
+ Hits         2559     2636      +77     
+ Misses       1375     1271     -104     
- Partials      671      698      +27     

Flag	Coverage Δ
macos	51.94% <50.00%> (+7.46%)	⬆️
ubuntu	52.81% <50.00%> (-0.61%)	⬇️
ubuntu_curl	53.10% <50.00%> (ø)
windows	56.65% <33.33%> (ø)

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[nmoinvaz]

It seems just like const change. What am I missing here?