bug: Ionic React Icon Type Regression

[elylucas]

Bug Report

There was a recent change to strongly type icons to {ios: string, md: string}, however, not all icons are of this type. Some are strings as well.

Ionic version:

[x] 4.11.8

Current behavior:
Icons that are just strings error when trying to assign them to the icon prop on IonIcon

Expected behavior:
Icons that are strings should work.

Steps to reproduce:

Related code:

insert short code snippets here

Other information:

Ionic info:

insert the output from ionic info here

[ionitron-bot]

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