std-switch: Remove the ripple element in the switch shadow tree

The element is unnecessary.  We can implement ripple effect in author's
stylesheets.

The test switch-appearance-customization.html has a sample
implementation of ripple effect.

Bug: 972476
Change-Id: Iaffe849d34f34614635906522c56ad42cd30e7fa
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1743434
Commit-Queue: Domenic Denicola <domenic@chromium.org>
Reviewed-by: Domenic Denicola <domenic@chromium.org>
Cr-Commit-Position: refs/heads/master@{#685314}
3 files changed