docs(migration): clarify data= vs text= parameter divergence in update()

Add a Note inside the Update Memory accordion explaining that OSS
Memory.update() takes data= while Platform MemoryClient.update()
(Python and JS/TS) takes text=, so migrating users know to rename
the keyword argument.

Addresses reviewer comment on oss-to-platform.mdx:224/391.

docs/migration/oss-to-platform.mdx

@@ -224,6 +224,10 @@ Note: `add()` and `delete()` methods remain unchanged. The `update()` method is
     client.update(memory_id="mem_123", text="Updated content")
     ```
     </CodeGroup>
+
+    <Note>
+      The parameter name differs between SDKs: OSS `Memory.update()` takes `data=`, while the Platform `MemoryClient.update()` (Python and JS/TS) takes `text=`. When migrating, rename this keyword argument.
+    </Note>
   </Accordion>
 </AccordionGroup>