Use any instead of interface{}

The keyword is available since Go 1.18 (see
https://pkg.go.dev/builtin#any).

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

libcontainer/specconv/spec_linux_test.go

@@ -676,7 +676,7 @@ func TestInitSystemdProps(t *testing.T) {
 	type expT struct {
 		isErr bool
 		name  string
-		value interface{}
+		value any
 	}
 
 	testCases := []struct {