Method deleteParentEntry

Method to encapsulate the process of deleting an entry (specifically the key and right child) from a parent node. If the parent becomes empty (no keys remaining), that indicates that it was the root node and should be replaced by its one remaining child. Otherwise, if it gets below minimum occupan

(TransactionId tid, HashMap<PageId, Page> dirtypages, 
			BTreePage leftPage, BTreeInternalPage parent, BTreeEntry parentEntry)