Use a single layout for CreateShortcut activity.

The old layout is inherited from LauncherActivity, which uses a
inconsistent theme and UI between phone and tablet. It's more consistent
to just use a single layout that matches setting theme.

Fixes: 32220535
Test: runtest --path packages/apps/Settings/tests/app/src/com/android/settings/CreateShortcutTest.java
Change-Id: I769d1404c82c2057bf021e4cf557e7cf397d92a7