chore(customPropTypes): remove customPropTypes.as

[layershifter]

We don't need anymore customPropTypes.as because it exists in prop-types as PropTypes.elementType.

[DustyTheBot]

	Warnings
⚠️	There are no updates provided to CHANGELOG. Ensure there are no publicly visible changes introduced by this PR.
⚠️	Package (or peer) dependencies changed. Make sure you have approval before merging!

Changed dependencies are detected.

Changed dependencies in packages/react-component-nesting-registry/package.json

package	before	after
prop-types	^15.6.1	^15.7.2

Changed dependencies are detected.

Changed dependencies in packages/react-component-event-listener/package.json

package	before	after
prop-types	^15.6.1	^15.7.2

Changed dependencies are detected.

Changed dependencies in packages/react-proptypes/package.json

package	before	after
prop-types	^15.6.1	^15.7.2

Changed dependencies are detected.

Changed dependencies in packages/react/package.json

package	before	after
prop-types	^15.6.1	^15.7.2

Changed dependencies are detected.

Changed dependencies in packages/react-component-ref/package.json

package	before	after
prop-types	^15.6.1	^15.7.2

Changed dependencies are detected.

Changed dependencies in packages/docs-components/package.json

package	before	after
prop-types	^15.6.1	^15.7.2

Generated by 🚫 dangerJS

[codecov]

Codecov Report

Merging #1775 into master will decrease coverage by <.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1775      +/-   ##
==========================================
- Coverage   69.82%   69.82%   -0.01%     
==========================================
  Files         873      873              
  Lines        7513     7512       -1     
  Branches     2183     2210      +27     
==========================================
- Hits         5246     5245       -1     
  Misses       2259     2259              
  Partials        8        8

Impacted Files	Coverage Δ
.../src/lib/accessibility/FocusZone/AutoFocusZone.tsx	100% <ø> (ø)	⬆️
...eact/src/lib/accessibility/FocusZone/FocusZone.tsx	89.65% <ø> (ø)	⬆️
.../src/lib/accessibility/FocusZone/FocusTrapZone.tsx	70.58% <ø> (ø)	⬆️
packages/react-proptypes/src/index.ts	34.26% <ø> (-0.46%)	⬇️
packages/react/src/lib/commonPropTypes.ts	100% <ø> (ø)	⬆️
...ackages/react/src/components/Provider/Provider.tsx	95.45% <ø> (ø)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update f736539...d5bd34a. Read the comment docs.