2021-December-05 - Prerelease - 2.6.491

Infra: remove update apt cache (#9866)

Apt cache update is not always strictly necessary. If needed,
we'll need to add it back in to run at an explicit time and
with retries.

Meanwhile removing the apt cache avoids errors like:

> fatal: [prerelease.triplea-game.org]: FAILED! => changed=false
  msg: 'Failed to update apt cache: '