fix(menus): Remove event on unmount

[ryanseddon]

Description

On menu unmount we had some code to remove the document event listener to support the click outside functionality.

Detail

We're in fact adding another listener again on unmount rather than removing it.

Checklist

• 👌 design updates are Garden Designer approved (add the
  designer as a reviewer)
• 💅 view component styling is based on a Garden CSS
  component
• 🌐 Styleguidist demo is up-to-date (yarn start)
• ⬅️ renders as expected with reversed (RTL) direction
• 💂‍♂️ includes new unit and snapshot tests
• 📒 any new files are included in the packages src/index.js export
• 📝 tested in Chrome, Firefox, Safari, Edge, and IE11

[seangoedecke]

🙇

[coveralls]

Pull Request Test Coverage Report for Build 501

• 1 of 1 (100.0%) changed or added relevant line in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.08%) to 96.089%

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Totals
Change from base Build 495:	-0.08%
Covered Lines:	1692
Relevant Lines:	1706

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💛 - Coveralls

[austingreendev]

Thanks for the fix!

[austingreendev]

I'm not sure how this decreased the number of tested lines since this is actually testing the desired action.

I think this one should be ok with pushing through.