Add `num_concurrent_runs` parameter to `gaia_solving_agent`

src/gaia_solving_agent/agent.py

@@ -150,4 +150,7 @@ gaia_solving_agent = FunctionAgent(
     You are a helpful assistant that uses tools to browse additional information and resources on the web to answer questions.
     """,
     name="gaia_solving_agent",
-    description="Agent that browse additional information and resources on the web.")
+    description="Agent that browse additional information and resources on the web.",
+    num_concurrent_runs=1,
+)
+