Drops required sign offs when amended commit is pushed to PR

[jeff-french]

Scenario:

• Opened PR that required general maintainer sign off as well as glob based sign off
• Received glob based sign off but not general maintainer
• Pushed amended commit to PR that only change a file that was part of the glob based sign off
• New FR comment only required glob-based sign off and NOT general maintainer.

Expected Result: New FR comment should still require general maintainer sign off and new glob based sign off.

[paultyng]

Probably the same as #7

We should probably indicate in the comment what sign offs are complete otherwise this will potentially become pretty confusing if it looks like you signed off but its not "counting" it. I'm not sure what that interaction should be.