Replace HTML entity with literal dash in Getting Started

Fixup for https://github.com/adobe/brackets/pull/8886/files#r16854363 and https://github.com/adobe/brackets/pull/8886/files#r16854679.
As the text is supposed to be read in the editor, a literal dash is way more legible.
I'm not sure, though, whether to use ` - ` or `—`.