Do we still need to browser sniff in `DockPanel` and `TabPanel`?

[afshin]

Since we no longer support Internet Explorer and now that Edge is based on WebKit, do we still need these? Can they be removed both here and from namespace Platform in @lumino/domutils?

lumino/packages/widgets/src/dockpanel.ts

Lines 379 to 382 in 2a30872

	// Flush the message loop on IE and Edge to prevent flicker.
	if (Platform.IS_EDGE || Platform.IS_IE) {
	MessageLoop.flush();
	}

lumino/packages/widgets/src/tabpanel.ts

Lines 326 to 330 in 2a30872

	// Flush the message loop on IE and Edge to prevent flicker.
	if (Platform.IS_EDGE || Platform.IS_IE) {
	MessageLoop.flush();
	}
	}

[fcollonval]

I'm 👍 to remove those

[vidartf]

I have Edge, so I can verify if you give me some steps to reliably test?