DOCS: Minor updates to handoffs.ipynb (#5665)

Updates:
- added missing backtick for formatting class name
- typo in user response example

Co-authored-by: Eric Zhu <ekzhu@users.noreply.github.com>

python/packages/autogen-core/docs/src/user-guide/core-user-guide/design-patterns/handoffs.ipynb

@@ -469,7 +469,7 @@
     "We have defined the AI agents, the Human Agent, the User Agent, the tools, and the topic types.\n",
     "Now we can create the team of agents.\n",
     "\n",
-    "For the AI agents, we use the {py:class}~autogen_ext.models.OpenAIChatCompletionClient`\n",
+    "For the AI agents, we use the {py:class}`~autogen_ext.models.OpenAIChatCompletionClient`\n",
     "and `gpt-4o-mini` model.\n",
     "\n",
     "After creating the agent runtime, we register each of the agent by providing\n",
@@ -705,7 +705,7 @@
       "Hello this is manager\n",
       "--------------------------------------------------------------------------------\n",
       "User:\n",
-      "Hi! Thanks for your service. I give you a 5 start!\n",
+      "Hi! Thanks for your service. I give you 5 stars!\n",
       "--------------------------------------------------------------------------------\n",
       "HumanAgent:\n",
       "Thanks.\n",