test: set standard date for date values used by DatePicker

[oh3vci]

Description

Because the new Date changed the date value each time the date changes, Test snapshots don't be matched.
So, I set the standard date merged DatePicker to dooboo-ui.

Related Issues

#337

Tests

just jest test

Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• Run yarn test or yarn test -u if you need to update snapshot.
• Run yarn lint
• I am willing to follow-up on review comments in a timely manner.

[codecov]

Codecov Report

Merging #340 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #340   +/-   ##
=======================================
  Coverage   83.25%   83.25%           
=======================================
  Files          37       37           
  Lines        1218     1218           
  Branches      367      367           
=======================================
  Hits         1014     1014           
  Misses         89       89           
  Partials      115      115           

[bumjoo]

Good job~!! Thanks.

[JeffGuKang]

LGTM