Exclude src/chainparamsseeds.h from formatting and autopep8 contrib/seeds/makeseeds.py

Summary: same as the title

Test Plan: nullptr

Reviewers: freetrader, kyuupichan, deadalnix, awemany, #bitcoin_abc

Reviewed By: deadalnix, #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D402