`dfs::Opts` does not serialize `benchOpts` field

[cwpearson]

tenzing/tenzing-dfs/src/dfs.cpp

Lines 11 to 14 in 86ecf95

	void to_json(nlohmann::json &j, const Opts &opts) {
	j.clear();
	j["dfs__Opts"]["maxSeqs"] = opts.maxSeqs;
	}