Fixes a regression where companion window would not scroll

[mejackreed]

Fixes a bug introduced in #2907

This was due to an update in react-rnd, introduced in v10.1.1, by updating re-resizable bokuweb/react-rnd@c3fa43f

This was due to an upstream bug fix in re-resizable that sets flexShrink: 0 for the parent div without a way to override it. https://github.com/bokuweb/re-resizable/pull/541/files

[codecov-io]

Codecov Report

Merging #2921 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #2921   +/-   ##
=======================================
  Coverage   93.21%   93.21%           
=======================================
  Files         157      157           
  Lines        2344     2344           
=======================================
  Hits         2185     2185           
  Misses        159      159

Impacted Files	Coverage Δ
src/components/CompanionWindow.js	93.75% <ø> (ø)	⬆️

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