zshenv: prefer en_DK.UTF-8 for LC_TIME.

en_DK.UTF-8 uses the ISO 8601 format for date, which is preferable to the
POSIX locale's US-style date.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
zshenv: remove useless commented code.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>