fix: update test error message expectations to match custom validator messages

Co-Authored-By: João <joao@crewai.com>

tests/test_allowed_agents.py

@@ -155,11 +155,11 @@ def test_allowed_agents_validation():
     )
     assert agent.allowed_agents is None
     
-    with pytest.raises(ValueError, match="Input should be a valid list"):
+    with pytest.raises(ValueError, match="allowed_agents must be a list or tuple of agent roles"):
         Agent(
             role="Test",
             goal="Test",
-            backstory="Test", 
+            backstory="Test",
             allowed_agents="invalid"
         )