Update AndroidManifest properties forBrowserPreferencesPage

The AndroidManifest was saying that the preferences activity was
handling orientation and keyboard visibility changes, which it does
not. This led to some strange layout issues, so remove the flags
from the manifest and let the system take care of these configuration
changes.

Change-Id: I0545b6d230363d6af3e4c6dedd4cd506c6f7ff21

AndroidManifest.xml

@@ -160,8 +160,7 @@
                   android:configChanges="orientation|keyboardHidden">
         </activity>
 
-        <activity android:name="BrowserPreferencesPage" android:label="@string/menu_preferences"
-                  android:configChanges="orientation|keyboardHidden">
+        <activity android:name="BrowserPreferencesPage" android:label="@string/menu_preferences">
         </activity>
 
         <activity android:name="BrowserHistoryPage" android:label=""