docs(openfeature-provider/go): small edit to install instruction (#133)

Author: nicklasl

openfeature-provider/go/README.md

@@ -16,6 +16,7 @@ A high-performance OpenFeature provider for [Confidence](https://confidence.spot
 
 ```bash
 go get github.com/spotify/confidence-resolver/openfeature-provider/go
+go mod tidy
 ```
 
 ## Requirements