Fix building docs when using LaTeX

[firefly-cpp]

Latexmk: Run number 1 of rule 'pdflatex'
This is pdfTeX, Version 3.141592653-2.6-1.40.25 (TeX Live 2023) (preloaded format=pdflatex)
restricted \write18 enabled.
entering extended mode
Latexmk: ====Undefined refs and citations with line #s in .tex file:
! LaTeX Error: Unicode character 🚀 (U+1F680)
! LaTeX Error: Unicode character 💪 (U+1F4AA)
! LaTeX Error: Unicode character 🔍 (U+1F50D)
! LaTeX Error: Unicode character ⏱ (U+23F1)
! LaTeX Error: Unicode character (U+FE0F)
! LaTeX Error: Unicode character 🚴 (U+1F6B4)
! LaTeX Error: Unicode character ‍ (U+200D)
And 89 more --- see log file 'sport-activities-features.log'