Fix URL protocol detection regex for file link= parameter

This regex looked something like /^(?i)bitcoin:|ftp://|ftps://|.../, which
meant the anchoring ^ only applied to the first name. This meant that any
link= value that happened to contain a URL protocol anywhere within it
(e.g. wikinews:Foo containing "news:") got incorrectly matched by this
regex.

Bug: 69317
Change-Id: Ide1c4f64137666db99f8e3b6816df01ef5099c8e
(cherry picked from commit fb7e8b876aa5bb327b53f4794e37b2016240975c)