Re-enable USE_LAST_RELEASE_AS_OLD_ISO on Jenkins after Tails 3.10 is released

#11501 (closed) required disabling USE_LAST_RELEASE_AS_OLD_ISO.

Revert commit 92312fb9eb560211c1591cfd0504435d1885104a in jenkins-jobs.git once 3.10 is out.

Original created by @intrigeri on 16053 (Redmine)

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information