docs: update guide to use mockgen with go run
This ensures the version tracked by go.mod gets used.
@@ -210,7 +210,7 @@ GoMock's `mockgen` tool is used to autogenerate mocks from interfaces.
As an example, to create a mock client for the `Configurator` interface defined in the [configurator](/pkg/configurator) package:
```bash
-mockgen -destination=pkg/configurator/mock_client.go -package=configurator github.com/openservicemesh/osm/pkg/configurator Configurator
+go run github.com/golang/mock/mockgen -destination=pkg/configurator/mock_client.go -package=configurator github.com/openservicemesh/osm/pkg/configurator Configurator
```
When a mocked interface is changed, the autogenerated mock code must be regenerated.
