Bump std++ once more.

7 jobs for ci/debug in 24 minutes and 31 seconds (queued for 1 second)
Status Job ID Name Coverage
  Build
passed #20175
fp
build-coq.8.7.1

00:05:08

passed #20174
fp
build-coq.8.7.2

00:05:00

canceled #20173
fp-timing
build-coq.8.8.0

passed #20172
fp
build-coq.8.8.1

00:04:56

passed #20171
fp
build-coq.8.8.2

00:04:45

canceled #20170
fp-timing
build-coq.8.9.dev

00:00:14

passed #20169
fp
build-coq.dev

00:24:31