new scope assignment warning in Distributed test

[vtjnash]

Caused by #49101 yesterday @tanmaykm

┌ Warning: Assignment to `wp` in soft scope is ambiguous because a global variable by the same name exists: `wp` will be treated as a new local. Disambiguate by using `local wp` to suppress this warning or `global wp` to assign to the existing global variable.
└ @ /cache/build/default-amdci5-6/julialang/julia-master/julia-0c240733b9/share/julia/stdlib/v1.10/Distributed/test/distributed_exec.jl:707
Distributed                                       (1) |   281.62 |   0.02 |  0.0 |      17.34 |   312.75