Fix keyboard not reacting to changed preferences

The callback might not be called if the "default" shared preferences is
different from the shared preferences actually used. This is unexpected
but seems to happen half of the time on Android 12.

Since f1ce6ab, this callback is critical to update the keyboard.
Restarting the application can no longer solve these issues.

srcs/juloo.keyboard2/SettingsActivity.java

@@ -17,7 +17,7 @@ public class SettingsActivity extends PreferenceActivity
     SharedPreferences prefs;
     // The preferences can't be read when in direct-boot mode. Avoid crashing
     // and don't allow changing the settings.
-    try { prefs = PreferenceManager.getDefaultSharedPreferences(this); }
+    try { prefs = getPreferenceManager().getSharedPreferences(); }
     catch (Exception _e) { fallbackEncrypted(); return; }
     addPreferencesFromResource(R.xml.settings);
     prefs.registerOnSharedPreferenceChangeListener(this.new OnPreferencesChange());