fix: remove CGO functions

These aren't actually used by anyone anywhere and they'll lead to build errors
if:

1. GCC isn't installed.
2. CGO_ENABLED isn't set to 0.

sockaddr_cgo.go

-package sockaddr
-
-import (
-	"C"
-	"unsafe"
-
-	sockaddrnet "github.com/libp2p/go-sockaddr/net"
-)
-
-// AnyToCAny casts a *RawSockaddrAny to a *C.struct_sockaddr_any
-func AnyToCAny(a *sockaddrnet.RawSockaddrAny) *C.struct_sockaddr_any {
-	return (*C.struct_sockaddr_any)(unsafe.Pointer(a))
-}
-
-// CAnyToAny casts a *C.struct_sockaddr_any to a *RawSockaddrAny
-func CAnyToAny(a *C.struct_sockaddr_any) *sockaddrnet.RawSockaddrAny {
-	return (*sockaddrnet.RawSockaddrAny)(unsafe.Pointer(a))
-}