docs(assistants): correct on_text_delta example (#1896)

Author: baballev

src/openai/lib/streaming/_assistants.py

@@ -243,7 +243,7 @@ def on_text_delta(self, delta: TextDelta, snapshot: Text) -> None:
         on_text_delta(TextDelta(value=" solution"), Text(value="The solution")),
         on_text_delta(TextDelta(value=" to"), Text(value="The solution to")),
         on_text_delta(TextDelta(value=" the"), Text(value="The solution to the")),
-        on_text_delta(TextDelta(value=" equation"), Text(value="The solution to the equivalent")),
+        on_text_delta(TextDelta(value=" equation"), Text(value="The solution to the equation")),
         """
 
     def on_text_done(self, text: Text) -> None: