Fix icon color in Toaster

[praveen-murali-ind]

• Fixes Icon classname and other props not reflected to the toastr icon #2379

Description

• The false value of the prop icon was ignored in the implementations before v9.0.2.
• After 9.0.2, the implementation is such that the icon is rendered as passed in the config.
• Since the false value was used to show the default icon set internally, replaced it with a function that returns null
  which solved the problem.
  • Code ref: https://github.com/fkhadra/react-toastify/blob/v8.0.1/src/components/Toast.tsx#L65-L75.
  • The if (icon === false) statement was never success for some reason.
• PR which addressed this issue: Fix closeButton/icon types/rendering fkhadra/react-toastify#758

Checklist

• I have made corresponding changes to the documentation.
• I have updated the types definition of modified exports.
• I have verified the functionality in some of the neeto web-apps.
• I have added tests that prove my fix is effective or that my feature works.
• I have added proper data-cy and data-testid attributes.
• I have added the necessary label (patch/minor/major - If package publish
  is required).

Reviewers

@deepakjosp _a

[deepakjosp]

@josephmathew900 _a please review.

[josephmathew900]

LGTM. @deepakjosp _a Please add the description and merge the PR.