ci(mise): go backend no longer experimental

[phm07]

The go backend is no longer experimental: https://github.com/jdx/mise/releases/tag/v2025.10.11

[apricote]

Looks like the mise version installed in ci is still from May.

[phm07]

Fix was already merged: #1286 #1287
Only needs a rebase

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 72.67%. Comparing base (9437efd) to head (6c2253f).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1283   +/-   ##
=======================================
  Coverage   72.67%   72.67%           
=======================================
  Files         302      302           
  Lines       10954    10954           
=======================================
  Hits         7961     7961           
  Misses       2125     2125           
  Partials      868      868           

Flag	Coverage Δ
e2e	51.85% <ø> (ø)
unit	67.63% <ø> (ø)

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