Fixing 404 for service definitions link

[moorara]

In this page

https://grpc.io/docs/reference/go/generated-code

If you click on Service Definitions you'll get 404.

[thelinuxfoundation]

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After the following items are addressed, please respond with a new comment here, and the automated system will re-verify.

• User @moorara isn't covered by a CLA. They will need to complete the form at https://identity.linuxfoundation.org/projects/cncf

Regards, CLA GitHub bot

[moorara]

Done!