fix: add divide by 0 use case

Author: thomasrockhu-codecov

app/test_calculator.py

@@ -28,4 +28,4 @@ def test_divide():
     assert Calculator.divide(1.0, 2.0) == 0.5
     assert Calculator.divide(0, 2.0) == 0
     assert Calculator.divide(-4, 2.0) == -2.0
-    # assert Calculator.divide(2.0, 0.0) == 'Cannot divide by 0'
+    assert Calculator.divide(2.0, 0.0) == 'Cannot divide by 0'