Remove Grassmann, since it was the wrong representation.

src/manifolds/GrassmannStiefel.jl

@@ -356,29 +356,6 @@ projecting it onto the tangent space at q.
 """
 vector_transport_to(::Grassmann, ::Any, ::Any, ::Any, ::ProjectionTransport)
 
-@doc raw"""
-    Weingarten(M::Grassmann, p, X, V)
-
-Compute the Weingarten map ``\mathcal W_p`` at `p` on the [`Grassmann`](@ref) `M` with
-respect to the tangent vector ``X \in T_p\mathcal M`` and the normal vector ``V \in N_p\mathcal M``.
-
-The formula is due to [AbsilMahonyTrumpf:2013](@cite) given by
-
-```math
-\mathcal W_p(X,V) = -\operatorname{ad}_p\bigl(\operatorname{ad}_V(X),
-```
-
-where $\operatorname{ad}_pX := [p,X] := pX - Xp$.
-"""
-Weingarten(::Grassmann, p, X, V)
-
-_ad(p, X) = p * X - X * p
-
-function Weingarten!(::Grassmann, Y, p, X, V)
-    Y .= -_ad(p, _ad(V, X))
-    return Y
-end
-
 @doc raw"""
     zero_vector(M::Grassmann, p)
 

src/manifolds/Stiefel.jl

@@ -346,7 +346,7 @@ Compute the retraction on the [`Stiefel`](@ref) that is based on the Cayley tran
 Using
 ````math
   W_{p,X} = \operatorname{P}_pXp^{\mathrm{H}} - pX^{\mathrm{H}}\operatorname{P_p}
-  \quad\text{where} 
+  \quad\text{where}
   \operatorname{P}_p = I - \frac{1}{2}pp^{\mathrm{H}}
 ````
 the formula reads

src/manifolds/StiefelEuclideanMetric.jl

@@ -136,8 +136,8 @@ end
     project(M::Stiefel,p)
 
 Projects `p` from the embedding onto the [`Stiefel`](@ref) `M`, i.e. compute `q`
-as the polar decomposition of $p$ such that $q^{\mathrm{H}q$ is the identity,
-where $\cdot^{\mathrm{H}}$ denotes the hermitian, i.e. complex conjugate transposed.
+as the polar decomposition of $p$ such that ``q^{\mathrm{H}}q`` is the identity,
+where ``\cdot^{\mathrm{H}}`` denotes the hermitian, i.e. complex conjugate transposed.
 """
 project(::Stiefel, ::Any, ::Any)
 
@@ -154,7 +154,7 @@ Project `X` onto the tangent space of `p` to the [`Stiefel`](@ref) manifold `M`.
 The formula reads
 
 ````math
-\operatorname{proj}_{\mathcal M}(p, X) = X - p \operatorname{Sym}(p^{\mathrm{H}}X),
+\operatorname{proj}_{T_p\mathcal M}(X) = X - p \operatorname{Sym}(p^{\mathrm{H}}X),
 ````
 
 where $\operatorname{Sym}(q)$ is the symmetrization of $q$, e.g. by