Fix dispatch for rdiv! with LU

[dkarrasch]

This method (added in #31853) was more specific than the one on line 493, which was added in #31285 at about the same time.

Fixes #55422.

[dkarrasch]

This will need to be backported manually...

[dkarrasch]

For the reproducer in the original issue, I get

julia> A = rand(1000,1000); @btime inv($A); @btime inv2($A); @btime inv3($A);
  25.634 ms (10 allocations: 8.13 MiB)
  38.917 ms (9 allocations: 15.27 MiB)
  37.542 ms (9 allocations: 15.27 MiB)

julia> inv(A) ≈ inv2(A) ≈ inv3(A)
true