Fix wrong docs for use_symbol_list

[IvoDD]

Simple docs change to reflect actual behavior.
See real behavior here:

ArcticDB/cpp/arcticdb/version/local_versioned_engine.cpp

Lines 188 to 191 in f9d955f

	if(use_symbol_list.value_or(cfg().symbol_list()))
	res = symbol_list().get_symbol_set(store());
	else
	res = list_streams(store(), version_map(), prefix, all_symbols.value_or(false));