FLT docs missing mathlib declarations

Stream: FLT

[Thomas Browning]

I noticed that the FLT docs contain mathlib declarations (e.g., https://imperialcollegelondon.github.io/FLT/docs/Mathlib/Data/Nat/Prime/Infinite.html#Nat.exists_infinite_primes), but don't let you search for mathlib declarations (e.g., type "Nat.exists_infinite_primes" in the search box). Whereas this works fine on the sphere eversion project (e.g., type "Nat.exists_infinite_primes" in the search box here: https://leanprover-community.github.io/sphere-eversion/docs/). I think this is problematic if we want upstreamed theorems in the FLT blueprint to point to mathlib.

[Rémy Degenne]

Same issue in the Brownian motion project, although it's not consistent. Sometimes it suddenly works again after a commit, and then breaks again after a few more (but I haven't seen it work in a while).