chore(wp): get rid of mathjax-based `[latex]` formatting

[marcelgerber]

So, I sneakily replaced our remaining three uses of the [latex] formatting declarator with MathML instead (which has universal browser support now, just not super-consistent rendering across browsers - looking at you, Safari):

• https://ourworldindata.org/excess-mortality-covid
• https://ourworldindata.org/history-of-poverty-data-appendix
• https://ourworldindata.org/mortality-risk-covid

This means that we can now get rid of the code for formatting these blocks :)

[owidbot]

Quick links (staging server): Site	Admin	Wizard

Login: ssh owid@staging-site-remove-mathjax

• Site-screenshots: https://github.com/owid/site-screenshots/compare/remove-mathjax
• SVG tester: https://github.com/owid/owid-grapher-svgs/compare/remove-mathjax

SVG tester:

Number of differences (default views): 0 ✅ Number of differences (all views): 0 ✅

Edited: 2024-06-19 14:40:32 UTC Execution time: 1.20 seconds