fix: check last fast-track request comment

[Mesteery]

Refs: nodejs/node#42141

[codecov]

Codecov Report

Merging #606 (98499c0) into main (919ec3b) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main     #606   +/-   ##
=======================================
  Coverage   84.10%   84.10%           
=======================================
  Files          37       37           
  Lines        4051     4051           
=======================================
  Hits         3407     3407           
  Misses        644      644           

Impacted Files	Coverage Δ
lib/pr_checker.js	98.44% <100.00%> (ø)

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