fix(terminal): stop file link provider throwing on printed URLs (#17767)

The terminal file link detector matches the '//host/path' left over once a
URL scheme is stripped (e.g. 'https://juliahub.com/products/dyad' -> match
'//juliahub.com/products/dyad'). Feeding that into URI.withPath throws a
UriError, since a path cannot begin with '//' without an authority component,
so the provider logged an error on every printed URL.

Skip such candidates in toURI: a '//'-prefixed path is a URL authority, not a
local file, and is left to the URL link provider. This removes the error log
and the false file link.

Signed-off-by: Dmitrij Rozdestvensky <dmitrij.rozdestvensky@juliahub.com>