Remove hard-coded reference to `species.id`

[jwalgran]

When converting a filter selection to a query, there is a hard-coded reference to species.id

otm-ios/OpenTreeMap/src/OTM/Controllers/OTMFilterListViewController.m

Lines 424 to 430 in 981168b

	- (NSDictionary *)queryParams {
	if ([self active]) {
	return @{ @"species.id": @{ @"IS": speciesId }};
	} else {
	return [NSDictionary dictionary];
	}
	}

Other filters read their field identifier dynamically from the instance info API response. Species should not be an exception.