Do not lint @generated files

Summary: This obviate the need to add specific exclusion rules for generated files.

Test Plan: Modify src/chainparamsseed.h in a way that won't make the linter happy, arc check that arc lint doesn't complain anyway.

Reviewers: schancel, freetrader, #bitcoin_abc

Reviewed By: schancel, #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D737