fix promote_op function #29739
This function had some weird and broken extraneous code,
close #28370 -- not really fixable, but just don't expect to get good results from inference and you should be all set.
I'm referring specifically to the addition of this method:
Previously, this result was achieved by defining that the result eltype was the typejoin of the input types with the result of calling
R = promote_op(add_sum, T, T) out = similar(A, R) cumsum!(out, A, dims=dims) return out
Since there's a