fix(jsdoc): controlText_ should have a protected access modifier.

[gjanblaszczyk]

Description

The controlText_ property should have a protected access modifier.
The PR is related to #7971

Requirements Checklist

• Feature implemented / Bug fixed
• If necessary, more likely in a feature request than a bug fix
  • Change has been verified in an actual browser (Chrome, Firefox, IE)
  • Unit Tests updated or fixed
  • Docs/guides updated
  • Example created (starter template on JSBin)
• Reviewed by Two Core Contributors

[codecov]

Codecov Report

Merging #7972 (e1e6425) into next (fa57723) will decrease coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             next    #7972      +/-   ##
==========================================
- Coverage   81.95%   81.94%   -0.02%     
==========================================
  Files         110      110              
  Lines        7333     7333              
  Branches     1767     1767              
==========================================
- Hits         6010     6009       -1     
- Misses       1323     1324       +1     

Impacted Files	Coverage Δ
src/js/big-play-button.js	27.58% <ø> (ø)
src/js/clickable-component.js	90.00% <ø> (ø)
...rol-bar/audio-track-controls/audio-track-button.js	87.50% <ø> (ø)
src/js/control-bar/fullscreen-toggle.js	94.11% <ø> (ø)
src/js/control-bar/mute-toggle.js	94.59% <ø> (ø)
src/js/control-bar/picture-in-picture-toggle.js	79.31% <ø> (ø)
src/js/control-bar/play-toggle.js	84.84% <ø> (ø)
...ar/playback-rate-menu/playback-rate-menu-button.js	100.00% <ø> (ø)
src/js/control-bar/seek-to-live.js	92.85% <ø> (ø)
...control-bar/text-track-controls/captions-button.js	81.25% <ø> (ø)
... and 9 more

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