remove "portrait-only" for MainActivity

Signed-off-by: Marcel Hibbe <dev@mhibbe.de>

app/src/main/AndroidManifest.xml

@@ -94,7 +94,6 @@
         <activity
             android:name=".activities.MainActivity"
             android:label="@string/nc_app_name"
-            android:screenOrientation="portrait"
             android:windowSoftInputMode="adjustPan">
             <intent-filter>
                 <action android:name="android.intent.action.MAIN" />