Remove custom source for MeshCatMechanisms from docs/Project.toml

Author: ferrolho

docs/Project.toml

@@ -4,6 +4,3 @@ MeshCat = "283c5d60-a78f-5afe-a0af-af636b173e11"
 MeshCatMechanisms = "6ad125db-dd91-5488-b820-c1df6aab299d"
 RigidBodyDynamics = "366cf18f-59d5-5db9-a4de-86a9f6786172"
 TORA = "a6da6c0f-f153-4ec6-bf42-6dc0ab733f84"
-
-[sources]
-MeshCatMechanisms = {rev = "hf/upstream-changes", url = "https://github.com/ferrolho/MeshCatMechanisms.jl"}