+force-all-tests suffix should use minus instead

In Jenkins, we replace the + with a -, which makes it more complicated to look for jobs in Jenkins just by copy-pasting. Since there is no benefit in using +, let's just stop it.

Context: I stumbled into that while working on Upgrade Tor Browser to 12.0.3-build1 (!1046 - merged). Yet another time, I copied the branch name, went to Jenkins, pressed Ctrl+F, Ctrl-V, and it couldn't find the branch. The same workflow work very well otherwise.