DOCS: Remove sphinxemoji extension as it is not used. (#145)

Author: MaxJPRey

doc/requirements.txt

@@ -7,7 +7,6 @@ sphinx-autobuild==2025.8.25
 sphinx-autodoc-typehints==3.6.0
 sphinxcontrib-websupport==2.0.0
 sphinx-copybutton==0.5.2
-sphinxemoji==0.3.1
 sphinx-gallery==0.20.0
 sphinx-notfound-page==1.1.0
 imageio==2.37.2