Re-enable USE_LAST_RELEASE_AS_OLD_ISO on Jenkins after Tails 3.10 is released

Originally created by @intrigeri on #16053 (Redmine)

tails/tails#11501 required disabling USE_LAST_RELEASE_AS_OLD_ISO.

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

Related issues

• Related to tails/tails#11501