docs(modal-wrapper): remove invalid prop, fix renderTriggerButtonIcon knob

[jendowns]

The ModalWrapper demo in the React storybook environment has an invalid prop triggerButtonIcon being passed to it.

Error text:

Warning: React does not recognize the `triggerButtonIcon` prop on a DOM element. If you intentionally want it to appear in the DOM as a custom attribute, spell it as lowercase `triggerbuttonicon` instead. If you accidentally passed it from a parent component, remove it from the DOM element.

---

This demo also has a default value of 'none' for the renderTriggerButtonIcon on page load, which is an invalid value & generates a console error in local development. (The error goes away when you use knobs to select an icon, because then the value being passed changes from 'none' to a valid icon).

Text of two console errors on page load:

Warning: Failed prop type: Invalid prop `renderTriggerButtonIcon` supplied to `ModalWrapper`.
    in ModalWrapper (created by Container)
    in Container (created by storyFn)
    in storyFn
    in ErrorBoundary

Warning: Failed prop type: Invalid prop `renderIcon` supplied to `Button`.
    in Button (created by ModalWrapper)
    in ModalWrapper (created by Container)
    in div (created by Story)
    in Story (created by Container)
    in div (created by Container)
    in StrictMode (created by Container)
    in Container (created by storyFn)
    in storyFn
    in ErrorBoundary

---

This PR proposes removing the invalid prop triggerButtonIcon and also updating the renderTriggerButtonIcon prop's knob logic so that, on page load, renderTriggerButtonIcon={undefined} (valid) and not renderTriggerButtonIco='none' (invalid)

Changelog

Changed

• change default value for renderTriggerButtonIcon prop knob. Now it will be renderTriggerButtonIcon={undefined} (valid) on page load, and not renderTriggerButtonIco='none' (invalid)

Removed

• remove triggerButtonIcon (not a valid prop)

Testing / Reviewing

I suggest running the storybook locally, and viewing the console in Chrome.

[jendowns]

Quick note: the line break + indentation is prettier formatting from the pre-commit hook 😅

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[asudoh]

LGTM 👍 - Thanks @jendowns!