Fix plot functionality (#2638)

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

tests/test_crew_plot.py

@@ -0,0 +1,20 @@
+import pytest
+
+from crewai.crew import Crew
+from crewai.agent import Agent
+
+
+def test_crew_plot_method_not_implemented():
+    """Test that trying to plot a Crew raises the correct error."""
+    agent = Agent(
+        role="Test Agent",
+        goal="Test Goal",
+        backstory="Test Backstory"
+    )
+    crew = Crew(agents=[agent], tasks=[])
+    
+    with pytest.raises(NotImplementedError) as excinfo:
+        crew.plot()
+    
+    assert "plot method is not available for Crew objects" in str(excinfo.value)
+    assert "Plot functionality is only available for Flow objects" in str(excinfo.value)