Fontify "print" and "exec" as functions in python-mode

This change was first made on master, but on closer consideration it
is better to fix this bug already in Emacs 28.1.

* lisp/progmodes/python.el (python-font-lock-keywords-level-2):
Fontify "print" and "exec" as functions, which is the case in
Python 3.  (Bug#43298)  Do not merge to master.

lisp/progmodes/python.el

@@ -555,9 +555,6 @@ class declarations.")
           "assert" "else" "if" "pass" "yield" "break" "except" "import" "class"
           "in" "raise" "continue" "finally" "is" "return" "def" "for" "lambda"
           "try"
-          ;; Python 2:
-          "print" "exec"
-          ;; Python 3:
           ;; False, None, and True are listed as keywords on the Python 3
           ;; documentation, but since they also qualify as constants they are
           ;; fontified like that in order to keep font-lock consistent between