Replace internal function by exported function in error messages

[Bisaloo]

readepi/R/check_dhis2_attributes-helpers.R

Lines 108 to 110 in b24e7e5

	stop("Provided attribute ids not found!\n
	Use readepi:::dhis2_make_api_request() function to view the list of
	available attributes")

This error message recommends using an internal function via :::, which is not something we should encourage. It is bad practice in R in general, and it mean that function is now effectively part of our public interface if we want to do changes.

Either this function can be called by users and it should be exported, and it shouldn't be called by users and we should propose an alternative in the error message