fix(ripple): eliminate double ripple effect on iOS

[peterminhk]

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This PR fix the issue that ripple effect is activated twice on iOS when zoom in page. see issue details: #4293

When tap a ripple surface on iOS Safari/Chrome below events are fired sequentially:

• pointerdown (activate ripple)
• touchstart (skipped)
• pointerup (deactivate ripple)
• mousedown (activate ripple again)

To solve this issue, we could find a solution to prevent mousedown after pointerup, but I had a doubt that why we had to handle mousedown event. There might be some sort of history, such as pointerdown was not supported on major browsers, but I couldn't figure out the actual reason (since this project was migrated from material-design-lite and there are no history remains about this) and, at this time, it looks like mousedown can be replaced with pointerdown.

Therefore, I removed mousedown/mouseup from ACTIVATION/DEACTIVATION event types and it worked well on various devices, including:

• Safari / Chrome on iOS (13.1.3)
• Safari / Chrome on macOS (10.15.1)
• Chrome on Android (9)
• Edge / Chrome on Windows 10

[codecov-io]

Codecov Report

:exclamation: No coverage uploaded for pull request base (master@a5dbd8a). Click here to learn what that means. The diff coverage is 100%.

@@            Coverage Diff            @@
##             master    #5305   +/-   ##
=========================================
  Coverage          ?   98.91%           
=========================================
  Files             ?      122           
  Lines             ?     6000           
  Branches          ?      772           
=========================================
  Hits              ?     5935           
  Misses            ?       64           
  Partials          ?        1

Impacted Files	Coverage Δ
packages/mdc-ripple/foundation.ts	100% <100%> (ø)

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[anlexN]

can we solve PR?