Update gatsby in /docs from 1.9.238 to 1.9.239

[dependencies]

Dependencies.io has updated gatsby (a npm dependency in /docs) from "1.9.238" to "1.9.239".

1.9.239

No content found. Please open an issue at https://github.com/dependencies-io/support if you think this content could have been found.

[codecov]

Codecov Report

Merging #3262 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #3262   +/-   ##
=======================================
  Coverage   36.21%   36.21%           
=======================================
  Files         443      443           
  Lines        9737     9737           
  Branches      912      891   -21     
=======================================
  Hits         3526     3526           
- Misses       5628     5672   +44     
+ Partials      583      539   -44

Impacted Files	Coverage Δ
app/vue/src/server/utils.js	0% <0%> (-100%)	⬇️
addons/knobs/src/angular/helpers.js	76.97% <0%> (ø)	⬆️
addons/storysource/src/loader/parsers/index.js	44.44% <0%> (ø)	⬆️
.../viewport/src/manager/components/RotateViewport.js	22.72% <0%> (ø)	⬆️
lib/core/src/client/preview/config_api.js	46.55% <0%> (ø)	⬆️
addons/jest/src/components/Indicator.js	0% <0%> (ø)	⬆️
addons/a11y/src/components/Report/Rules.js	0% <0%> (ø)	⬆️
addons/actions/src/lib/types/symbol/index.js	81.25% <0%> (ø)	⬆️
lib/ui/src/modules/shortcuts/actions/shortcuts.js	18.84% <0%> (ø)	⬆️
app/react/src/client/preview/element_check.js	67.64% <0%> (ø)	⬆️
... and 56 more

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