Remove leftover from the schnorr experiment
Summary: Removed the residual file from the schnorr experiment: src/bench_schnorr_verify.c
Test Plan:
make check
python3 qa/pull-tests/rpc-tests.py
Reviewers: O1 Bitcoin ABC, #bitcoin_abc, deadalnix, MattBitprim
Reviewed By: O1 Bitcoin ABC, #bitcoin_abc, deadalnix
Subscribers: deadalnix, freetrader
Differential Revision: https://reviews.bitcoinabc.org/D247