[R] [CI] Add ENV TZ to docker files

[asfimport]

Does adding ENV TZ UTC to docker files prevent the following (harmless) error we see from time to time on CI?

https://github.com/rocker-org/rocker/blob/master/r-edge/gcc-11/Dockerfile#L37-L38 suggests it might

System has not been booted with systemd as init system (PID 1). Can't operate.
Failed to connect to bus: Host is down
Warning in system("timedatectl", intern = TRUE) :
  running command 'timedatectl' had status 1

Reporter: Jonathan Keane / @jonkeane
Assignee: Jonathan Keane / @jonkeane

PRs and other links:

• GitHub Pull Request #10703

_{Note: This issue was originally created as ARROW-13215. Please see the migration documentation for further details.}

[asfimport]

Neal Richardson / @nealrichardson:
Issue resolved by pull request 10703
#10703