Fix alignment of cheat sheet example (#15039)

In `cheat_sheep_py3.rst` functions examples, there is one function
example misaligned with to other examples in the code block. This PR
just removes leading space.

docs/source/cheat_sheet_py3.rst

@@ -103,10 +103,10 @@ Functions
    def show(value: str, excitement: int = 10) -> None:
        print(value + "!" * excitement)
 
-    # Note that arguments without a type are dynamically typed (treated as Any)
-    # and that functions without any annotations not checked
-    def untyped(x):
-        x.anything() + 1 + "string"  # no errors
+   # Note that arguments without a type are dynamically typed (treated as Any)
+   # and that functions without any annotations not checked
+   def untyped(x):
+       x.anything() + 1 + "string"  # no errors
 
    # This is how you annotate a callable (function) value
    x: Callable[[int, float], float] = f