Fonts that print underscore beyond a cell's height don't render anything in the DOM renderer

[Tyriar]

VS Code issue: microsoft/vscode#159110
Same issue but on the top: #5240

Not a regression, just noticed while investigating microsoft/vscode#158497

It should be this_that:

The font in question Droid Sans Mono, probably DejaVu Sans Mono too which default on a lot of Linux distros write the underscore below the natural height of the char.