net: remove redundant comment on isWildcard

R=golang-dev, dave
CC=golang-dev
https://golang.org/cl/11985043

src/pkg/net/unixsock_posix.go

@@ -103,7 +103,6 @@ func (a *UnixAddr) family() int {
 	return syscall.AF_UNIX
 }
 
-// isWildcard reports whether a is a wildcard address.
 func (a *UnixAddr) isWildcard() bool {
 	return a == nil || a.Name == ""
 }