De-Coreify /doc/tor.md
Summary:
Change Core to ABC in /doc/tor.md
Part of task T59
Test Plan: N/A
Reviewers: deadalnix, freetrader, O1 Bitcoin ABC, #bitcoin_abc
Reviewed By: deadalnix, O1 Bitcoin ABC, #bitcoin_abc
Differential Revision: https://reviews.bitcoinabc.org/D314