CL 52430 added logic to skip the testZoneAbbr test in locales where
the timezone does not have a three-letter name, because the following
line
Parse(RFC1123, t1.Format(RFC1123))
failed for timezones with only numeric names (like -07).
Since Go 1.11, Parse supports the parsing of timezones with numeric
names (this was implemented in CL 98157), so we can now run the test
unconditionally.