Add c++ balise for TF1 documentation

[pamputt]

Hello, on the new TF1 documentation page, could you add some “c++ balise” for the examples C to E. There are already such balises for the examples A and B.
Thank you in advance.

[pamputt]

Fixed by lmoneta in these commits:

• https://github.com/root-mirror/root/commit/9b27e38ffadbbf1b5a77de7275cbdf6072878c56
• https://github.com/root-mirror/root/commit/b8e996976c838ced8a9e0c19ebeff295fd9c244e
  Thank you