LPS-45694 The 'x' in the search field appears on top of opened iframes

Hey @Robert-Frampton,

Here is an update for https://issues.liferay.com/browse/LPS-45694. 

I asked Nate about the high z-index value set for the button-search-cancel. He said that the high value is used to make sure that the icon will appear on top of the iframe. So a value greater than the iframe's z-index is used. An example of this is the sign-in portlet. However, when I changed the z-index to a small value, the icon still appears fine. Even if it's rendered inside an iframe, the icon will show up on top of the iframe without any issue. That's why I'm removing the z-index from the addInputCancel. Please let me know if this fix will break any other stuff that I'm not aware of.  Thanks!