The entire mechanic for preparing spells has changed, so the feature to convert spell slots into spontaneous Heal spells is no longer needed as a separate feature - it's now just possible.
Instead of preparing spells into spell slots, you simply prepare a list of spells for the day. Wizards prepare from their spells known in their spellbook, Clerics, Druids and Paladins prepare from their entire class list. As a Cleric, you have some spells always prepared based on your domain, and then each day you choose a number of spells from you class list equal to your level + your wisdom modifier and prepare those to be cast with any of your spell slots.
Essentially, prepared casting now works like spontaneous casting, with the daily preparation determining what spells you can spontaneously cast that day. So if you chose Cure Wounds or Healing Word as one of your prepared spells, any of your available spell slots can be used to cast it, and you gain the benefits of upcasting into higher spell slots spontaneously as well.
This has the side effect of making prepared casting objectively superior to known spellcasting, as the number of spells you can prepare is larger than the number of spells known by known casters (Bards, Rangers, Sorcerers and Warlocks).
ALSO, Clerics aren't really dedicated healers anymore, they're meant to have more freedom with what you want to do. However they also aren't very effective healers, because healing in 5e is very inefficient outside of yo-yo combat healing (waiting until your allies hit 0 before healing them is generally most effective, as it's pretty hard to get killed and you fight just as effectively at 1 hp as you do 100).
The Life Domain Cleric is the only one that can really specialize as a healer, and even then, your healing won't keep up with the damage taken in most cases.