[rpc] deprecate ancient softforks' information from getblockchaininfo

Summary:
I don't think anyone cares about this, and in fact it is a bit annoying
since it fills a typical 80x25 terminal with essentialy useless information
that causes the important stuff to scroll out of view.

Test Plan:
make check
test_runner.py --extended
read bitcoin-cli help getblockchaininfo
try with bitcoind -deprecatedrpc=getblockchaininfo

Reviewers: deadalnix, jasonbcox, Fabien, #bitcoin_abc, nakihito

Reviewed By: Fabien, #bitcoin_abc, nakihito

Subscribers: nakihito

Differential Revision: https://reviews.bitcoinabc.org/D3358