[Dev][Go] Add grpc generated go files to rat exclusion list

[asfimport]

The RAT check is failing https://github.com/apache/arrow/runs/1161033600

Reporter: Krisztian Szucs / @kszucs
Assignee: Krisztian Szucs / @kszucs

PRs and other links:

• GitHub Pull Request #8273

_{Note: This issue was originally created as ARROW-10092. Please see the migration documentation for further details.}

[asfimport]

Krisztian Szucs / @kszucs:
Issue resolved by pull request 8273
#8273