[rb] update firefox test to allow system access for changing content context

Firefox 138 now requires this

Author: titusfortner

Diff for: rb/spec/integration/selenium/webdriver/firefox/driver_spec.rb

@@ -143,7 +143,8 @@ module Firefox
         end
 
         it 'can get and set context' do
-          reset_driver!(prefs: {'browser.download.dir': 'foo/bar'}) do |driver|
+          reset_driver!(args: ['-remote-allow-system-access'],
+                        prefs: {'browser.download.dir': 'foo/bar'}) do |driver|
             expect(driver.context).to eq 'content'
 
             driver.context = 'chrome'