Merge pull request #6699 from tjhei/doxygen-mathjax

doxygen: fix formulas using good mathjax location

Author: gassmoeller

doc/options.dox

@@ -1168,7 +1168,7 @@ USE_MATHJAX            = YES
 # However, it is strongly recommended to install a local
 # copy of MathJax from http://www.mathjax.org before deployment.
 
-MATHJAX_RELPATH        = http://cdn.mathjax.org/mathjax/latest
+MATHJAX_RELPATH        = https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.9/
 
 # The MATHJAX_EXTENSIONS tag can be used to specify one or MathJax extension
 # names that should be enabled during MathJax rendering.