[JuliaLowering] Disable lone-local error
Triage has agreed (#57483) that this can be an error, but is probably not the
kind of change to make through JuliaLowering; I see at least one instance in
the pkgeval (HYPRE.jl, which comments "Silence of the Langs(erver)")
The message should also be fixed if we bring it back: local declarations have no
effect outside of a scope or top-level block.