Clarify hardware extension Scratch Link modal language

[benjiwheeler]

Some reports (e.g., from LLK Brazil team) that the wording of the hardware troubleshooting modal is confusing.

Current text:
"Make sure you have Scratch Link installed and running"

Current design:

(In Brazilian Portuguese:)

Some users have reported that this is confusing. When users haven't heard of Scratch Link, they seem to not realize that we're talking about a separate program that must be downloaded.

One user asked, "Is it saying that Scratch needs to link to Scratch?"

Maybe we could provide more context by linking to the appropriate hardware page on our site (MicroBit page, EV3 page, etc.)

[benjiwheeler]

FWIW, my sense is that this is a design/UX question we should come back to after launch.

[thisandagain]

/cc @ericrosenbaum @evhan55 @carljbowman