[rb] firefox scroll by amount is only failing on mac

Author: titusfortner

rb/spec/integration/selenium/webdriver/action_builder_spec.rb

@@ -316,7 +316,9 @@ module WebDriver
       end
 
       describe '#scroll_by', only: {browser: %i[chrome edge firefox]} do
-        it 'scrolls by given amount', except: {browser: :firefox, reason: 'scrolls insufficient number of pixels'} do
+        it 'scrolls by given amount', except: {browser: :firefox,
+                                               platform: :macosx,
+                                               reason: 'scrolls insufficient number of pixels'} do
           driver.navigate.to url_for('scrolling_tests/frame_with_nested_scrolling_frame_out_of_view.html')
           footer = driver.find_element(tag_name: 'footer')
           delta_y = footer.rect.y.round