fix(TextArea): fix autoHeight calculate wrong value on long text

[WiNloSt]

Calculate content height without taking a vertical scroll bar into account.

fixes #2173

[WiNloSt]

Tests failed at

adds/removes body classes "dimmable dimmed" on mount/unmount
HeadlessChrome 0.0.0 (Linux 0.0.0)
AssertionError: document.body should not have class "dimmable", but it has class="dimmable dimmed": expected true to equal false

Not sure if it has anything to do with my code, but tests passes on my machine.

[codecov-io]

Codecov Report

Merging #2199 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #2199      +/-   ##
==========================================
+ Coverage   99.73%   99.73%   +<.01%     
==========================================
  Files         151      151              
  Lines        2622     2624       +2     
==========================================
+ Hits         2615     2617       +2     
  Misses          7        7

Impacted Files	Coverage Δ
src/addons/TextArea/TextArea.js	100% <100%> (ø)	⬆️

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[layershifter]

Retrigger build, now CI passing

[levithomason]

Thanks folks!

[levithomason]

Released in semantic-ui-react@0.75.1