net: do not try to remove the LocalAddr of a unix socket
TestUnixAndUnixpacketServer deferred a call to os.Remove on the local
address of a dialed unix domain socket, in an attempt to remove the
socket from the server. However, that call appears to be neither
necessary nor correct.
In this test, the file that needs to be unlinked is the one attached
to the listener — but the listener's Close method already does that
(see the Unlink call in (*UnixListener).close), so there is no need
for the test itself to do the same.
Moreover, the local address is not something that is sensible to
delete — on Linux, it is empirically always the literal string "@" —
and the Addr returned by c.LocalAddr is not reliably non-nil on all
platforms (see #34611).
Since we don't need to do anything with the local address, we shouldn't.
At best, this is a benign Remove of a file that doesn't exist anyway;
at worst, it is a nil-panic.