Consolidate suggested import path for go thrift library to git.apache.org in docs and code

https://github.com/apache/thrift/blob/master/lib/go/README.md suggests to use the following import path for go thrift library:

git-wip-us.apache.org/repos/asf/thrift.git/lib/go/thrift

However thrift compiler uses different import path in the generated files by default:

git.apache.org/thrift.git/lib/go/thrift

To avoid confusion it would be good to use a single import path both in the generated code and in the user documentation.