Use UTC timezone in formatting too for knobs test

[tmeasday]

Issue: #2859

Previously I fixed the TZ of the date itself but not the timezone we are formatting relative to.

What I did

Fixed both.

How to test

Run storyshots tests

[Hypnosphi]

Please apply locale and tz to vue-kitchen-sink example as well

[codecov]

Codecov Report

Merging #2861 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #2861   +/-   ##
=======================================
  Coverage   35.82%   35.82%           
=======================================
  Files         428      428           
  Lines        9423     9423           
  Branches      969      959   -10     
=======================================
  Hits         3376     3376           
- Misses       5392     5409   +17     
+ Partials      655      638   -17

Impacted Files	Coverage Δ
lib/core/src/client/manager/index.js	0% <0%> (ø)	⬆️
addons/events/src/components/Event.js	38.55% <0%> (ø)	⬆️
addons/links/src/react/components/link.js	78.78% <0%> (ø)	⬆️
lib/core/src/client/manager/preview.js	0% <0%> (ø)	⬆️
addons/knobs/src/components/types/Array.js	34.14% <0%> (ø)	⬆️
addons/actions/src/lib/util/prepareArguments.js	57.14% <0%> (ø)	⬆️
...ents/stories_panel/stories_tree/tree_decorators.js	34.37% <0%> (ø)	⬆️
...res__/update-addon-info/update-addon-info.input.js	0% <0%> (ø)	⬆️
addons/graphql/src/components/FullScreen/index.js	0% <0%> (ø)	⬆️
addons/actions/src/lib/types/infinity/index.js	80% <0%> (ø)	⬆️
... and 52 more

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[tmeasday]

It looks like there is a date in the Angular stories (although it uses the built in date formatting), and the polymer tests

[tmeasday]

LMK what you think we should do in the angular case @Hypnosphi

[Hypnosphi]

Let's keep it as is until we hit any issues with angularshots