Change the default pgAdmin theme to System. #9093

Author: adityatoshniwal

docs/en_US/release_notes_9_8.rst

@@ -20,10 +20,12 @@ Bundled PostgreSQL Utilities
 New features
 ************
 
+  | `Issue #9093 <https://github.com/pgadmin-org/pgadmin4/issues/9093>`_ -  Change the default pgAdmin theme to System.
 
 Housekeeping
 ************
 
+  | `Issue #7448 <https://github.com/pgadmin-org/pgadmin4/issues/7448>`_ -  Remove usage of BrowserFS as it is deprecated.
 
 Bug fixes
 *********

web/pgadmin/misc/__init__.py

@@ -80,7 +80,7 @@ def register_preferences(self):
 
         self.preference.register(
             'user_interface', 'theme',
-            gettext("Theme"), 'options', 'light',
+            gettext("Theme"), 'options', 'system',
             category_label=PREF_LABEL_USER_INTERFACE,
             options=theme_options,
             control_props={