Fix documentation: eigenspace does not return a Vector (#2034)

src/matrix.jl

@@ -255,11 +255,12 @@ end
 
 @doc raw"""
     eigenspace(M::MatElem{T}, lambda::T; side::Symbol = :left)
-      where T <: FieldElem -> Vector{MatElem{T}}
+      where T <: FieldElem -> MatElem{T}
 
-Return a basis of the eigenspace of $M$ with respect to the eigenvalue $\lambda$.
-If side is `:right`, the right eigenspace is computed, i.e. vectors $v$ such that
-$Mv = \lambda v$. If side is `:left`, the left eigenspace is computed, i.e. vectors
+Return a matrix whose rows (if `side == :left`) or columns (if `side == :right`)
+give a basis of the eigenspace of $M$ with respect to the eigenvalue $\lambda$.
+If `side` is `:right`, the right eigenspace is computed, i.e. vectors $v$ such that
+$Mv = \lambda v$. If `side` is `:left`, the left eigenspace is computed, i.e. vectors
 $v$ such that $vM = \lambda v$.
 """
 function eigenspace(M::MatElem{T}, lambda::T; side::Symbol = :left) where T <: FieldElem