lt_LT locale: Update abbreviated month names (bug 22932).

A GNOME translator asked to use the same abbreviated month names
as provided by CLDR.  This sounds reasonable.  See the discussion:
https://bugzilla.gnome.org/show_bug.cgi?id=793645#c27

	[BZ #22932]
	* localedata/locales/lt_LT (abmon): Synchronize with CLDR.