Fix small typo on default config doc page

[mvargeson]

Issue: N/A

What I did

Fixed a small typo duplicate ;; on default config doc page

How to test

N/A

[codecov]

Codecov Report

Merging #1226 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1226   +/-   ##
=======================================
  Coverage   13.72%   13.72%           
=======================================
  Files         207      207           
  Lines        4640     4640           
  Branches      506      505    -1     
=======================================
  Hits          637      637           
  Misses       3576     3576           
  Partials      427      427

Impacted Files	Coverage Δ
lib/ui/src/modules/ui/routes.js	0% <0%> (ø)	⬆️
app/react-native/src/preview/story_kind.js	0% <0%> (ø)	⬆️
app/react/src/client/preview/render.js	0% <0%> (ø)	⬆️
lib/ui/src/modules/ui/components/layout/usplit.js	38.7% <0%> (ø)	⬆️
addons/storyshots/src/test-bodies.js	0% <0%> (ø)	⬆️
addons/knobs/src/KnobManager.js	38.57% <0%> (ø)	⬆️
addons/storyshots/src/require_context.js	0% <0%> (ø)	⬆️
addons/storyshots/src/storybook-channel-mock.js	0% <0%> (ø)	⬆️
app/react-native/src/bin/storybook-start.js	0% <0%> (ø)	⬆️
lib/ui/src/modules/ui/configs/handle_routing.js	28.94% <0%> (ø)	⬆️
... and 11 more

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[ndelangen]

Thank you @mvargeson @renemichel !!