Update the `launchMode` for the `GodotApp` activity to allow other activities to be part of the same task

For details, see https://developer.android.com/guide/topics/manifest/activity-element#lmode

(cherry picked from commit 14428c8d5b068fd59a0ae03a2a8a20d3ffae86a2)

platform/android/java/app/AndroidManifest.xml

@@ -35,7 +35,7 @@
             android:name=".GodotApp"
             android:label="@string/godot_project_name_string"
             android:theme="@style/GodotAppSplashTheme"
-            android:launchMode="singleInstance"
+            android:launchMode="singleInstancePerTask"
             android:excludeFromRecents="false"
             android:exported="true"
             android:screenOrientation="landscape"