Feature request: Reduce gemspec requirements for `google-protobuf`

[alexus37]

Hi there,

We’re excited to install the appollo-federation-ruby for our project! However, we’re currently using google-protobuf: 3.14. Would it be possible to relax the constraints in the gemspec file?

https://github.com/Gusto/apollo-federation-ruby/blob/51af77bce4e48e864e97b849053f1e5992edcd6a/apollo-federation.gemspec#L31C3-L31C59

Eg something along these lines?

spec.add_runtime_dependency 'google-protobuf', '>= 3.0', '< 4.0'