android: Use same theme for SettingsActivity

Don't use another theme for the SettingsActivity
than for the rest of the app.

I don't see any big visual change when opening
the activity at least in an API 36 (Android 16)
AVD anyway (with an additional
local revert of commit 9d1e76f7da
to prevent a deadlock when opening documents that is unrelated
to this change here)
and this will simplify maintenance and
adding support for targetSdkVersion 35 where edge-to-edge
is enabled by default [1].

[1] https://developer.android.com/about/versions/15/behavior-changes-15#window-insets

Change-Id: I1e5dccfefe930d34a8b315df04a6f07f050a5b54
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/187626
Reviewed-by: Michael Weghorn <m.weghorn@posteo.de>
Tested-by: Jenkins

android/source/AndroidManifest.xml

@@ -92,7 +92,6 @@
 
         <activity
             android:name=".SettingsActivity"
-            android:theme="@style/Theme.AppCompat.DayNight.DarkActionBar"
             android:label="@string/app_name_settings">
         </activity>