Describe the doc issue

\tableofcontents fixed in Doxygen 1.8.16 (doxygen/doxygen#6791 (comment))

For example, https://docs.opencv.org/4.x/d0/dcc/tutorial_non_linear_svms.html has no table at this moment (Doxygen 1.8.13):

https://docs.opencv.org/4.x/d0/dcc/tutorial_non_linear_svms.html
https://docs.opencv.org/5.x/d0/dcc/tutorial_non_linear_svms.html

Doxygen 1.9.1:

Fix suggestion

Update Doxygen for public documentation