Use actionlint Docker image

[martincostello]

• Use actionlint from a Docker image for consistency with other repos.
• Bump actionlint to v1.6.26.

[codecov]

Codecov Report

Merging #1251 (8b029d6) into main (5e342ad) will increase coverage by 0.24%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #1251      +/-   ##
==========================================
+ Coverage   86.15%   86.39%   +0.24%     
==========================================
  Files         138      138              
  Lines        3330     3330              
==========================================
+ Hits         2869     2877       +8     
+ Misses        461      453       -8     

Flag	Coverage Δ
linux	86.15% <ø> (ø)
macos	54.17% <ø> (ø)
windows	54.17% <ø> (ø)

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see 2 files with indirect coverage changes

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