wpcom/v2 endpoints do not autocomplete

[sirbrillig]

To reproduce:

1. Open the dev console.
2. Change the endpoint path to wpcom/v2 (see screenshot below).
3. Type /sites into the path field.

What I expected: to see a list of /sites endpoints.

What I saw instead: nothing happens, but there's an error in the dev console.

I believe the line in question is this un-guarded regexp reference.

(Originally I reported this in https://github.com/Automattic/rest-api-console2/issues/26 but I think it was the wrong repo.)