docs: update object.data API docs

Author: Alan Shaw

SPEC/OBJECT.md

@@ -126,17 +126,18 @@ A great source of [examples][] can be found in the tests for this API.
 
 | Type | Description |
 | -------- | -------- |
-| `Promise<Buffer>` | A Buffer with the data that the MerkleDAG node contained |
+| `AsyncIterable<Buffer>` | An async iterable that yields Buffer objects with the data that the MerkleDAG node contained |
 
 **Example:**
 
 ```JavaScript
-const multihash = 'QmPb5f92FxKPYdT3QNBd1GKiL4tZUXUrzF4Hkpdr3Gf1gK'
+const cid = 'QmPb5f92FxKPYdT3QNBd1GKiL4tZUXUrzF4Hkpdr3Gf1gK'
 
-const data = await ipfs.object.data(multihash)
-console.log(data.toString())
-// Logs:
-// some data
+for await (const chunk of ipfs.object.data(cid)) {
+  console.log(chunk.toString())
+  // Logs:
+  // some data
+}
 ```
 
 A great source of [examples][] can be found in the tests for this API.