The current tag wiki for heap implies it is indeed a synonym of heap-memory. However, a heap also refers to a particular data structure which may or may not be related to memory allocation:
A heap data structure should not be confused with the heap which is a
common name for dynamically allocated memory. The term was originally
used only for the data structure.
As such, IMHO the correct course of action would be to retag questions to heap-memory where appropriate, but not turn heap into a synonym. Then, if there's any questions that are related to the data structure, an edit to the heap tag wiki (or creation of, say, a heap-data-structure tag) would be in order.