Card redesign: 'enabled by default' label instead of user count for default extensions

Created by: AlicjaSuska

Description

For the extensions that are enabled by default we should display 'enabled by default' instead of the number of users.

Details & context

@Joelkw 's comment in Figma explains the context:

So we originally didn't build tracking for enabled-by-default extensions like git-extras and the language extensions, but we can. Since it's enabled by default, we could either: a) say "enabled by default" instead of a user number b) say some number like "10,000+" based on our total users c) start tracking and just have to separately keep a list of enabled by default extensions I am leaning towards a in the short term and c in the longer term, especially if we build "usage" tracking rather than enable/activations tracking in the medium term

Decision: a short term, c long term.