Add JSON API support for timezone update (#2806)

* Add JSON API support for timezone update

* Simplify timezone controller to just head :no_content

* Use PUT instead of PATCH in timezone tests to match docs

* Use PATCH instead of PUT for timezone endpoint

Reverts tests to use patch and updates docs heading to PATCH
for consistency.

test/controllers/my/timezones_controller_test.rb

@@ -12,4 +12,11 @@ class My::TimezonesControllerTest < ActionDispatch::IntegrationTest
     patch my_timezone_path, params: { timezone_name: "America/New_York" }
     assert_equal time_zone, users(:kevin).reload.timezone
   end
+
+  test "update as JSON" do
+    assert_not_equal ActiveSupport::TimeZone["America/Chicago"], users(:kevin).timezone
+    patch my_timezone_path, params: { timezone_name: "America/Chicago" }, as: :json
+    assert_response :no_content
+    assert_equal ActiveSupport::TimeZone["America/Chicago"], users(:kevin).reload.timezone
+  end
 end