Properly escape ' in sed script.

2 jobs for !307 with robbert/empty_iff in 4 minutes and 34 seconds (queued for 8 seconds)
latest detached
Status Name Job ID Coverage
  Build
passed build-coq.8.10.2 #137719
fp

00:04:34

passed build-coq.8.13.2-mr #137718
fp

00:04:22