Update Jenkins config for upgraded plugins

I upgraded plugins, some of them caused config changes, let's get back
in sync! I'm really happy to see that the disk space usage plugin has
stopped storing its data in config.xml, that gets rid of so much noise!

Auditors: alan

Test Plan:
Already running on jenkins.ka.org
Remove FORCE_INDEX_CHANGES flag in Jenkins builds

This is now handled entirely by deploy.py and so this option is no
longer useful. A default deploy will always update indexes, and a
non-default will not.

Auditors: alan
CC: csilvers

Test Plan:
Already live on jenkins.ka.org
Change cron entry for sync-captions job

This changed some time ago, just bringing config up to par.

Test Plan:
Already live on jenkins.ka.org