script: ceph-backport no longer launches firefox

script: ceph-backport no longer launches firefox

this script uses `pgrep firefox` to determine whether a browser is open,
and will pause the ceph-backport script waiting for the commands
`firefox "${backport_pr_url}` and `firefox "${redmine_url}"` to exit

on Fedora release 41 with Mozilla Firefox 133.0, `pgrep firefox` always
finds a process even if no browser window is open:

> /usr/lib64/firefox/firefox --dbus-service /usr/bin/firefox

the ceph-backport script prints these URLs as output, so it's easy
enough to open them in a browser where desired

Signed-off-by: Casey Bodley <cbodley@redhat.com>