browser(firefox): do not use system colors for controls (#1838)

Author: pavelfeldman

browser_patches/firefox/BUILD_NUMBER

@@ -1 +1 @@
-1083
+1084

browser_patches/firefox/preferences/playwright.cfg

@@ -3,6 +3,9 @@
 // Use light theme by default.
 pref("ui.systemUsesDarkTheme", 0);
 
+// Do not use system colors - they are affected by themes.
+pref("ui.use_standins_for_native_colors", true);
+
 pref("dom.push.serverURL", "");
 pref("services.settings.server", "");
 pref("browser.safebrowsing.provider.mozilla.updateURL", "");