crypto/tls: fix TestLinkerGC test

A test that checks if "tls.(*Conn)" appears in any symbol's name.
tls.Conn is a type, so the string "tls.(*Conn)" can only appear
in the name of a method of Conn. But the test code doesn't use
any of the methods. Not sure why this needs to be live. In
particular, the linker is now able to prune all methods of Conn.
Remove this requirement. In fact, just drop the only_conn test
case, as simply allocating a type doesn't necessarily bring
anything live.

Change-Id: I754291b75d38e1465b5291b4dea20806615d21b3
Reviewed-on: https://go-review.googlesource.com/c/go/+/257973
Trust: Cherry Zhang <cherryyz@google.com>
Trust: Tobias Klauser <tobias.klauser@gmail.com>
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Filippo Valsorda <filippo@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>
Reviewed-by: Jeremy Faller <jeremy@golang.org>

link_test.go

@@ -41,19 +41,6 @@ func main() {}
 				"type.crypto/tls.serverHandshakeState",
 			},
 		},
-		{
-			name: "only_conn",
-			program: `package main
-import "crypto/tls"
-var c = new(tls.Conn)
-func main() {}
-`,
-			want: []string{"tls.(*Conn)"},
-			bad: []string{
-				"type.crypto/tls.clientHandshakeState",
-				"type.crypto/tls.serverHandshakeState",
-			},
-		},
 		{
 			name: "client_and_server",
 			program: `package main