fix(switch): Fix switch toggling on IE and Edge

[rlfriedman]

Fixes #3111, tested in Chrome, Firefox, IE, and Edge. The issue seems to have come from some sort of interaction between the display flex on the parent of the thumb and the rest of the styling (for IE and Edge).

[codecov-io]

Codecov Report

Merging #3119 into feat/switch-update will not change coverage.
The diff coverage is n/a.

@@                 Coverage Diff                 @@
##           feat/switch-update    #3119   +/-   ##
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  Coverage               98.49%   98.49%           
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  Files                     101      101           
  Lines                    4316     4316           
  Branches                  540      540           
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  Hits                     4251     4251           
  Misses                     65       65

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[kfranqueiro]

Question: why is the z-index: 1 needed on __thumb? If I remove that and do nothing else, this problem seems to go away. I'm not sure if that causes any other problems...?

[rlfriedman]

z-index: 1 is needed to position the thumb above the ripple underlay.

[kfranqueiro]

Oh, because ripple typically acts as an overlay. Did design specifically indicate that the ripple is supposed to appear in back of the thumb for switch?

I'd check with them first to make sure we're doing the right thing, but otherwise I'll approve this if that's correct.

[rlfriedman]

Yeah, I confirmed with design that for switch the ripple should be under the thumb.