lint: fix attribute networkSecurityConfig is only used in API level 24 and higher (current min is 14)

src/main/AndroidManifest.xml

@@ -19,7 +19,8 @@
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 -->
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
-          package="com.owncloud.android">
+    xmlns:tools="http://schemas.android.com/tools"
+    package="com.owncloud.android">
 
     <!-- GET_ACCOUNTS is needed for API <= 22.
         For API >= 23 results in the addition of CONTACTS group to the list of permissions that may be
@@ -75,7 +76,8 @@
         android:networkSecurityConfig="@xml/network_security_config"
         android:supportsRtl="true"
         android:installLocation="internalOnly"
-        android:manageSpaceActivity="com.owncloud.android.ui.activity.ManageSpaceActivity">
+        android:manageSpaceActivity="com.owncloud.android.ui.activity.ManageSpaceActivity"
+        tools:ignore="UnusedAttribute">
         <activity
             android:name=".ui.activity.FileDisplayActivity"
             android:label="@string/app_name"