LLM / CB: simplify condition

[ilya-lavrenov]

sg->has_finished() already assumes that request can be OOM or it's handle can be dropped

openvino.genai/src/cpp/src/sequence_group.hpp

Lines 297 to 309 in ca6f5cb

	size_t num_finished_seqs() const {
	return std::count_if(m_sequences.begin(), m_sequences.end(), [this] (Sequence::CPtr seq) {
	return seq->has_finished() || seq->out_of_memory() || handle_dropped();
	});
	}
	size_t num_running_seqs() const {
	return num_total_seqs() - num_finished_seqs();
	}
	bool has_finished() const {
	return num_running_seqs() == 0;
	}