build: disable libsecp256k1 benchmarks
build: disable libsecp256k1 benchmarks

These were previously disabled, but upstream changed to having benchmarks enabled by default
in https://github.com/bitcoin-core/secp256k1/pull/480 and we pulled that change as part of #15703.


Former-commit-id: 78f9dadb35c102a45ba9a424368ac470fc045b8e
syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin