DocumentsStorageProvider: fix build error due to missing import

Signed-off-by: Álvaro Brey <alvaro.brey@nextcloud.com>

app/src/main/java/com/owncloud/android/providers/DocumentsStorageProvider.java

@@ -40,7 +40,6 @@ import android.os.ParcelFileDescriptor;
 import android.provider.DocumentsContract;
 import android.provider.DocumentsProvider;
 import android.util.Log;
-import android.util.SparseArray;
 import android.widget.Toast;
 
 import com.nextcloud.client.account.User;
@@ -86,6 +85,7 @@ import java.net.URLEncoder;
 import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
+import java.util.Map;
 import java.util.Objects;
 import java.util.concurrent.Executor;
 import java.util.concurrent.Executors;