Removing extensions::FeatureSwitch which is no longer used

chrome/browser/extensions/extension_install_prompt.cc

Index: chrome/browser/extensions/extension_install_prompt.cc
diff --git a/chrome/browser/extensions/extension_install_prompt.cc b/chrome/browser/extensions/extension_install_prompt.cc
index 0af21940338ff4a6ee58dd25248b0c960ba20dba..940457a18f314174c9c7a9c19e57cced9988fd6d 100644
--- a/chrome/browser/extensions/extension_install_prompt.cc
+++ b/chrome/browser/extensions/extension_install_prompt.cc
@@ -737,8 +737,7 @@ void ExtensionInstallPrompt::ConfirmInstall(
   // disabled because in that case, we don't show the dangerous download UI, so
   // we need the UI confirmation.
   if (extension->is_theme()) {
-    if (extension->from_webstore() ||
-        extensions::FeatureSwitch::easy_off_store_install()->IsEnabled()) {
+    if (extension->from_webstore()) {
       delegate->InstallUIProceed();
       return;
     }