Docs: Maven repo missing latest versions

Referencing #9475

The Readme is referencing codegen client [paths for v2.x.x and 3.x.x-rc](http://central.maven.org/maven2/io/swagger/swagger-codegen-cli/). Can you update the v3 path to [the correct one](https://repo1.maven.org/maven2/io/swagger/codegen/v3/swagger-codegen-cli/) please?

