Revert exported tag that may not be needed

Author: JulianKast

android/sdl_android/src/androidTest/AndroidManifest.xml

@@ -16,8 +16,7 @@
 
     <application android:debuggable="true">
         <uses-library android:name="android.test.runner" />
-        <activity android:name=".managers.lockscreen.SDLLockScreenActivity"
-            android:exported="true"/>
+        <activity android:name=".managers.lockscreen.SDLLockScreenActivity" />
     </application>
 
 </manifest>