use go1.22.6 to build fulcio

[cpanato]

• use go1.22.6 to build fulcio

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 50.35%. Comparing base (cf238ac) to head (fdbae13).
Report is 192 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1793      +/-   ##
==========================================
- Coverage   57.93%   50.35%   -7.58%     
==========================================
  Files          50       70      +20     
  Lines        3119     4180    +1061     
==========================================
+ Hits         1807     2105     +298     
- Misses       1154     1843     +689     
- Partials      158      232      +74     

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[haydentherapper]

Let's cut 1.6.4 after this as well to pick up the reverted change #1791

[cpanato]

@haydentherapper i will merge and prepare the release notes