[Wi-Fi NetworkRequest] Don't need to have code to test theme

Per setting team's suggestion, don't need to test theme, so remove
related code in testing.

Bug: N/A
Test: N/A, Just remove test code.
Change-Id: If0ca632506b554a4471b5d25f07ab27a078de92e

tests/robotests/src/com/android/settings/wifi/NetworkRequestDialogActivityTest.java

@@ -32,7 +32,6 @@ import android.os.Bundle;
 import androidx.annotation.Nullable;
 import androidx.appcompat.app.AlertDialog;
 
-import com.android.settings.R;
 import com.android.settings.testutils.shadow.ShadowAlertDialogCompat;
 import com.android.settings.wifi.NetworkRequestErrorDialogFragment.ERROR_DIALOG_TYPE;
 import com.android.settingslib.wifi.WifiTracker;
@@ -127,12 +126,4 @@ public class NetworkRequestDialogActivityTest {
 
         verify(mActivity).finish();
     }
-
-    @Test
-    public void launchActivityDialog_shouldApplyAlertDialogTheme() {
-        final NetworkRequestDialogActivity activity = Robolectric
-                .setupActivity(NetworkRequestDialogActivity.class);
-
-        assertThat(activity.getThemeResId()).isEqualTo(R.style.Theme_AlertDialog);
-    }
 }