[#705] Fix setReturnFocus option as function not getting prev node

[stefcameron]

Fixes #705

When the setReturnFocus option is a function, it should get the
previously focused node prior to activation as its first parameter,
yet it was not because of the special handling in focus-trap-react
for trap deactivation.

PR Checklist

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• Issue being fixed is referenced.
• Source changes maintain:
  • Stated browser compatibility.
  • Stated React compatibility.
• Unit test coverage added/updated.
• E2E test coverage added/updated.
• Prop-types added/updated.
• Typings added/updated.
• Changes do not break SSR:
  • Careful to test typeof document/window !== 'undefined' before using it in code that gets executed on load.
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[changeset-bot]

🦋 Changeset detected

Latest commit: ebea041

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
focus-trap-react	Patch

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[codecov]

Codecov Report

Merging #706 (ebf2a32) into master (42ce4ab) will decrease coverage by 0.57%.
The diff coverage is 82.35%.

❗ Current head ebf2a32 differs from pull request most recent head ebea041. Consider uploading reports for the commit ebea041 to get more accurate results

@@            Coverage Diff             @@
##           master     #706      +/-   ##
==========================================
- Coverage   93.33%   92.76%   -0.58%     
==========================================
  Files           1        1              
  Lines         150      152       +2     
  Branches       63       65       +2     
==========================================
+ Hits          140      141       +1     
- Misses         10       11       +1     

Impacted Files	Coverage Δ
src/focus-trap-react.js	92.76% <82.35%> (-0.58%)	⬇️

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