Fix unused variable warning
We need to call `in_time_zone` to test that it isn't modifying the receiver but since the variable isn't used it raises a warning so add an assertion to make Ruby think it's being used.
|@@ -1001,6 +1001,7 @@ def test_time_in_time_zone_doesnt_affect_receiver|
|with_env_tz 'Europe/London' do|
|time = Time.local(2000, 7, 1)|
|time_with_zone = time.in_time_zone('Eastern Time (US & Canada)')|
|+ assert_equal Time.utc(2000, 6, 30, 23, 0, 0), time_with_zone|
|assert_not time.utc?, 'time expected to be local, but is UTC'|