fix(date): remove datepicker prop-type

[jordan-a-young]

Before submitting a pull request, please make sure the following is done:

1. Fork the repository and create your branch from master.
2. Run yarn in the repository root.
3. If you've fixed a bug or added code that should be tested, add tests!
4. Ensure the test suite passes (yarn test). Tip: yarn test --watch TestName is helpful in development.
5. Make sure your code passed the conventional commits check. Read more about conventional commits

[codecov[bot]]

Codecov Report

Merging #1273 (cc0a143) into master (060fff9) will increase coverage by 1.12%. The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1273      +/-   ##
==========================================
+ Coverage   90.44%   91.57%   +1.12%     
==========================================
  Files          10        8       -2     
  Lines         513      273     -240     
  Branches      143       93      -50     
==========================================
- Hits          464      250     -214     
+ Misses         49       23      -26     

Impacted Files	Coverage Δ
packages/date/src/Date.js	93.05% <ø> (ø)
packages/date/src/DateRange.js	92.52% <ø> (ø)

... and 16 files with indirect coverage changes