[Settings] Code refactor - remove unused import lines

Remove some unused import lines within source code based on
https://source.android.com/setup/contribute/code-style

Bug: 182867979
Test: build pass
Change-Id: I76dbcfa9e5b435b2838401dfee15b12f472d07d0

src/com/android/settings/network/telephony/MobileDataDialogFragment.java

@@ -29,7 +29,6 @@ import androidx.appcompat.app.AlertDialog;
 import com.android.settings.R;
 import com.android.settings.core.instrumentation.InstrumentedDialogFragment;
 
-
 /**
  * Dialog Fragment to show dialog for "mobile data"
  *