make IAM HTML listener more clear in scope and effect

[torossian97]

Why are you making this change? (required)

It may be unclear to some users what the HTML listener affects. We're calling out that DnD messages will also be affected.

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[Bucimis]

we should also say what the listener doesn't apply to - namely traditional IAMs

[torossian97]

Added a suggested edit below

[torossian97]

Suggested change

	This listener applies to __both__ messages built with custom HTML and messages created using the Drag-and-Drop (DnD) editor.
	This listener applies to __both__ messages built with custom HTML and messages created using the Drag-and-Drop (DnD) editor. It does not apply to traditional IAMs.