[backport-1.10] Fix dispatch for rdiv! with LU (#56415)

Backport of #55764.

Author: dkarrasch

stdlib/LinearAlgebra/src/lu.jl

@@ -713,7 +713,7 @@ function ldiv!(adjA::AdjointFactorization{<:Any,<:LU{T,Tridiagonal{T,V}}}, B::Ab
     return B
 end
 
-rdiv!(B::AbstractMatrix, A::LU) = transpose(ldiv!(transpose(A), transpose(B)))
+rdiv!(B::AbstractMatrix, A::LU{T,Tridiagonal{T,V}}) where {T,V} = transpose(ldiv!(transpose(A), transpose(B)))
 
 # Conversions
 AbstractMatrix(F::LU) = (F.L * F.U)[invperm(F.p),:]