Serialization stdlib: Replace a call to `Core.memoryref` with `Core.memoryrefnew` (#61137)
The Serialization stdlib has the following function:
https://github.com/JuliaLang/julia/blob/e46125f569f43e28261d1b55a0d85aacceee499a/stdlib/Serialization/src/Serialization.jl#L1445-L1450
As far as I can tell, there is no method matching
`Core.memoryref(x::MemoryRef, i::Int, true::Bool)` (called on line
1448).[^1]
[^1]: This issue was detected by JET.
I think this should be a call to `Core.memoryrefnew(x::MemoryRef,
i::Int, true::Bool)` instead, which is what this PR does.