Add synchronize trigger to ready label check (#2354)

SUMMARY:
Triggers the ready label check each time new commits are pushed to a pr.

Looking at #2350 it
seems like there is still an issue with our ready check system.
1. The first commit was added
2. The ready label was added and second commit
(7d7ebd2) was pushed, this caused the
ready check to run and pass
3. Further commits were added but the ready check was never retriggered
4. "ready-label-check Expected — Waiting for status to be reported" is
blocking merge, despite the most recent run of the ready check passing.

It seems like required checks may need to run and pass on the most
recent commit for github to allow the merge. This pr causes subsequent
commits to re-trigger the ready check workflow.


TEST PLAN:
Merge and see if this fixes the problem. It can't make it worse since
this just causes the check to run more often.

Signed-off-by: Fynn Schmitt-Ulms <fschmitt@redhat.com>
Co-authored-by: Dipika Sikka <dipikasikka1@gmail.com>

Author: fynnsu

.github/workflows/ready-label-check.yaml

@@ -8,6 +8,7 @@ on:
       - unlabeled
       - opened
       - reopened
+      - synchronize
 
 concurrency:
   group: ${{ github.workflow }}-${{ github.ref }}