feat(python): add "return" patterns to @indent_end

`return ...` is usually the last line of a
function/statement, so mark some possible patterns of `return` with
`@indent_end` to dedent the line after it

tests/indent/python/return_dedent.py

@@ -0,0 +1,16 @@
+def a():
+    return
+
+def a():
+    return True
+
+def a():
+    return (1, 2, 3)
+
+def a():
+    return x.y.z
+
+def a():
+    return (
+        1, 2, 3
+    )