libbpf: replace Detach() with Destroy() for KABPFLink

Detach was introduced as a temporary empty method.

After discussions

aquasecurity/libbpfgo#74
aquasecurity/libbpfgo#78

it was understood that it isn't feasible to use Detach() directly.

In the meantime, Destroy() was implemented by a third contributor.

aquasecurity/libbpfgo#69

This get rids of the previous empty function making room for the
Destroy() wrapper.

libbpf.go

@@ -343,7 +343,7 @@ func (l *KABPFLink) Program() *KABPFProgram {
  return l.bpfProg
 }
 
-// Detach link
-func (l *KABPFLink) Detach() error {
- return nil
+// Destroy link
+func (l *KABPFLink) Destroy() error {
+ return l.bpfLink.Destroy()
 }