Revert "cmd/go: update TestScripts/svn to not depend on TZ database"

Revert "cmd/go: update TestScripts/svn to not depend on TZ database"

This reverts CL 447335.

Reason for revert: broke test on solaris-amd64-oraclerel, which does have a TZ database but has a non-UTC system time zone.

Change-Id: Id61f182d331fc5ca8475845fe0ebf3f1d105d8a3
Reviewed-on: https://go-review.googlesource.com/c/go/+/447756
Reviewed-by: Than McIntosh <thanm@google.com>
Auto-Submit: Bryan Mills <bcmills@google.com>
TryBot-Bypass: Bryan Mills <bcmills@google.com>
Run-TryBot: Bryan Mills <bcmills@google.com>
Reviewed-by: Quim Muntal <quimmuntal@gmail.com>