fix: Fix MenuButton not receiving focus after Menu closes

[diegohaz]

This issue exists on master:

1. Open https://reakit.io/storybook/?path=/story/menu--menu-with-dialog
2. Focus menu button
3. Press ArrowUp
4. Press Escape

Focus will not return to the menu button. Now do the same on https://deploy-preview-692--reakit.netlify.app/storybook/?path=/story/menu--menu-with-dialog (this PR).

Does this PR introduce a breaking change?

No.

[codesandbox-ci]

This pull request is automatically built and testable in CodeSandbox.

To see build info of the built libraries, click here or the icon next to each commit SHA.

Latest deployment of this branch, based on commit 6646cc6:

Sandbox	Source
Reakit	Configuration

[ariakit-bot]

Deploy preview for reakit ready!

Built with commit 6646cc6

https://deploy-preview-692--reakit.netlify.app

[github-actions]

Size Change: 0 B

Total Size: 250 kB

ℹ️ View Unchanged

Filename	Size	Change
packages/reakit-playground/dist/reakit-playground.min.js	186 kB	0 B
packages/reakit-system-bootstrap/dist/reakit-system-bootstrap.min.js	19.2 kB	0 B
packages/reakit-system-palette/dist/reakit-system-palette.min.js	8.84 kB	0 B
packages/reakit-system/dist/reakit-system.min.js	2.21 kB	0 B
packages/reakit-utils/dist/reakit-utils.min.js	3.16 kB	0 B
packages/reakit/dist/reakit.min.js	31.1 kB	0 B

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[codecov]

Codecov Report

Merging #692 into master will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #692   +/-   ##
=======================================
  Coverage   95.58%   95.58%           
=======================================
  Files         151      151           
  Lines        2788     2788           
  Branches      727      727           
=======================================
  Hits         2665     2665           
  Misses        123      123           

Impacted Files	Coverage Δ
packages/reakit/src/Menu/MenuButton.ts	100.00% <100.00%> (ø)

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