Use system version of Go

[mmlb]

Description

Drop go from shell.nix (for now) and use the system's go binary.

Why is this needed

CI is currently breaking because of conflicting go versions.
The better fix would be cutting over fully to nix in CI or reverting this commit once actions/setup-go#175 is merged and released.

How Has This Been Tested?

CI

How are existing users impacted? What migration steps/scripts do we need?

CI isn't broken and PRs can be merged.

[mmlb]

Pretty sure I'll have to merge this manually once github lets me.

[codecov]

Codecov Report

Merging #582 (04a8431) into main (b18b238) will increase coverage by 1.24%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main     #582      +/-   ##
==========================================
+ Coverage   34.76%   36.01%   +1.24%     
==========================================
  Files          44       44              
  Lines        3348     3207     -141     
==========================================
- Hits         1164     1155       -9     
+ Misses       2085     1959     -126     
+ Partials       99       93       -6     

Impacted Files	Coverage Δ
http-server/http_handlers.go	6.80% <0.00%> (+0.15%)	⬆️

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