docs: replace main() with init() in rlimit example

This is probably how it should be used in production, and staticcheck
started complaining about main() being unused.

Signed-off-by: Timo Beckers <[email protected]>

Author: ti-mo

docs/examples/rlimit_test.go

@@ -5,7 +5,7 @@ package examples
 // DocRlimit {
 import "github.com/cilium/ebpf/rlimit"
 
-func main() {
+func init() {
 	if err := rlimit.RemoveMemlock(); err != nil {
 		panic(err)
 	}