remove using HTTP PROXY from environment variable

[aviramha]

remove using HTTP PROXY from environment variable, matching kubectl's behavior.

I found out that kubectl doesn't care for the HTTP_PROXY environment variable, probably for security reasons (a way to have plaintext requests?)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 75.3%. Comparing base (c0fe0c8) to head (08fda05).
Report is 4 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #1587     +/-   ##
=======================================
- Coverage   75.3%   75.3%   -0.0%     
=======================================
  Files         82      82             
  Lines       7331    7329      -2     
=======================================
- Hits        5519    5517      -2     
  Misses      1812    1812             

Files with missing lines	Coverage Δ
kube-client/src/config/file_loader.rs	85.8% <ø> (-0.5%)	⬇️

[clux]

This sounds sensible to me if the go side does not do it.
CC @goenning who currently has a related issue under #1203.

[goenning]

Ship it :)