Update insert-css to 2.0.0

[Hypnosphi]

Issue: #2157

The only breaking change is handling of falsy values:
https://github.com/substack/insert-css/pull/28/files

[codecov]

Codecov Report

Merging #2234 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #2234   +/-   ##
=======================================
  Coverage   22.16%   22.16%           
=======================================
  Files         268      268           
  Lines        5875     5875           
  Branches      707      707           
=======================================
  Hits         1302     1302           
  Misses       4024     4024           
  Partials      549      549

Impacted Files	Coverage Δ
app/vue/src/server/config/babel.js	0% <0%> (-100%)	⬇️
app/vue/src/server/babel_config.js	0% <0%> (-77.42%)	⬇️
app/react/src/server/babel_config.js	77.41% <0%> (+77.41%)	⬆️
app/react/src/server/config/babel.js	100% <0%> (+100%)	⬆️

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[codecov-io]

Codecov Report

Merging #2234 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #2234   +/-   ##
=======================================
  Coverage   22.16%   22.16%           
=======================================
  Files         268      268           
  Lines        5878     5878           
  Branches      718      711    -7     
=======================================
  Hits         1303     1303           
- Misses       4013     4033   +20     
+ Partials      562      542   -20

Impacted Files	Coverage Δ
addons/storyshots/src/require_context.js	0% <0%> (ø)	⬆️
app/react-native/src/bin/storybook-start.js	0% <0%> (ø)	⬆️
lib/ui/src/modules/shortcuts/actions/shortcuts.js	6.25% <0%> (ø)	⬆️
...ponents/left_panel/stories_tree/tree_decorators.js	33.33% <0%> (ø)	⬆️
lib/ui/src/modules/ui/libs/filters.js	47.36% <0%> (ø)	⬆️
addons/info/src/components/PropTable.js	21.36% <0%> (ø)	⬆️
addons/knobs/src/components/types/Boolean.js	11.62% <0%> (ø)	⬆️
addons/knobs/src/KnobManager.js	31.37% <0%> (ø)	⬆️
lib/ui/src/modules/ui/containers/left_panel.js	25.71% <0%> (ø)	⬆️
lib/components/src/navigation/menu_link.js	0% <0%> (ø)	⬆️
... and 15 more

---

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Δ = absolute <relative> (impact), ø = not affected, ? = missing data
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