Update something about the triangulation docs for py 3.14 with absence of `triangle` wheel

[TimMonko]

@TimMonko currently, triangle is actually used to build the docs, so this change requires updating this code:

https://napari.org/stable/guides/triangulation.html

docs/docs/guides/triangulation.md

Line 37 in d3bccd3

from triangle import triangulate

to make it optional, or the build will fail when it gets to that page. Personally, I like having four results there, so I don't know what the best path forward is.

Originally posted by @jni in napari/napari#8703 (comment)