Mark keyless verification as not experimental

[lcarva]

https://issues.redhat.com/browse/HACBS-2079

[codecov]

Codecov Report

Merging #907 (642ce3d) into main (7d4cbd5) will increase coverage by 6.45%.
The diff coverage is 100.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #907      +/-   ##
==========================================
+ Coverage   79.06%   85.51%   +6.45%     
==========================================
  Files          57       64       +7     
  Lines        4843     5172     +329     
==========================================
+ Hits         3829     4423     +594     
+ Misses       1014      749     -265     

Flag	Coverage Δ
acceptance	69.30% <100.00%> (?)
generative	48.93% <ø> (ø)
integration	60.16% <ø> (ø)
unit	70.69% <100.00%> (-0.01%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files Changed	Coverage Δ
cmd/validate/image.go	94.33% <100.00%> (+4.47%)	⬆️
internal/policy/policy.go	86.34% <100.00%> (+2.48%)	⬆️

... and 29 files with indirect coverage changes