systemd: Expand Systemd::Timer::Interval pattern

This matches all the time spans documented in `man systemd.time`. It's a
superset of the existing pattern.

Hosts: mwmaint1002.eqiad.wmnet,people2003.codfw.wmnet
Change-Id: I6b103e67ea05e64f74aec07b5fa0292f436d9a18
diff --git a/modules/systemd/types/timer/interval.pp b/modules/systemd/types/timer/interval.pp
index a64fe73..a361bee 100644
--- a/modules/systemd/types/timer/interval.pp
+++ b/modules/systemd/types/timer/interval.pp
@@ -1 +1 @@
-type Systemd::Timer::Interval = Pattern[/\A(\d+\s*(us|ms|s|sec|m|min|h|hour|d|w|M|y)\s*)+\Z/]
+type Systemd::Timer::Interval = Pattern[/\A(\d+\s*(usec|[uμ]s|msec|ms|seconds?|sec|s|minutes?|min|m|hours?|hr|h|days?|d|weeks?|w|months?|M|years?|y)\s*)+\Z/]