internal/lsp: fix link handling for links without schemes
internal/lsp: fix link handling for links without schemes

Unfortunately, this can't be tested until golang/go#35880 is resolved,
because only the third-party xurls library detects links without
schemes.

Change-Id: I620581d6ce99c79ae89f3f22ea8ee634c3850a8e
Reviewed-on: https://go-review.googlesource.com/c/tools/+/214280
Run-TryBot: Rebecca Stambler <d7cf11e5f299d88ea8348366a9fc4f7c335c3afa@golang.org>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Heschi Kreinick <e89ab2b172855aa0ad01c40c4d8a3535a61ac68a@google.com>

golang/tools,golang/tools,golang/tools,golang/tools,golang/tools