Fix spin_matrices call in StructureFactor

Hopefully the last commit required to make docs build, at least

src/StructureFactors/StructureFactors.jl

@@ -125,7 +125,7 @@ function StructureFactor(sys::System{N}; Δt, nω, measperiod,
             # SQTODO: Make this use the more optimized expected_spin function
             # Doing this will also, by necessity, allow users to make the same
             # type of optimization for their vector-valued observables.
-            observables = LinearMap{ComplexF64}.(spin_matrices(N))
+            observables = LinearMap{ComplexF64}.(spin_matrices(;N))
         end
     else
         # If it was given as a list, preserve the user's preferred