[core] fix(Toaster): disable invasive focus management

[adidahiya]

Fixes #5032

Changes proposed in this pull request:

Disable the Overlay shouldReturnFocusOnClose feature for toasts, since it doesn't make sense to do this kind of focus management for toasts.

Reviewers should focus on:

Pretty simple change, you can see that it only affects these lines of code execution for the Toaster Overlay:

blueprint/packages/core/src/components/overlay/overlay.tsx

Lines 616 to 618 in b80422a

	if (this.props.shouldReturnFocusOnClose && this.lastActiveElementBeforeOpened instanceof HTMLElement) {
	this.lastActiveElementBeforeOpened.focus();
	}

Screenshot

N/A

[blueprint-bot]

[core] fix(Toaster): disable invasive focus management

Previews: documentation | landing | table | modern colors demo