en/Mathjax docs changes

In MDL-44780 the new Mathjax filter was turned on by default in Moodle 2.7. The following user documentation changes are suggested.

https://docs.moodle.org/26/en/Performance_recommendations

I would suggest a link to https://docs.moodle.org/26/en/Performance_settings at the end of the "Performance of different Moodle modules" section in the form of a link like "Click here for more detailed information on performance related Moodle settings".

https://docs.moodle.org/26/en/Performance_settings

There current text is...

Check your filters. Having too many filters active can have serious effects on server load, especially on lower-end systems. The number of active filters has a direct effect on the perceived latency of your site; that is the time taken for each page impression.

My suggestion is...

Check your filters. Having too many filters active can have serious effects on server load, especially on lower-end systems. The number of active filters has a direct effect on the perceived latency of your site; that is the time taken for each page impression. Check if any of the filters can be disabled. For example, if your site does not need to be able to display mathematical equations you can disable the Mathjax filter.