[REPL] Autocompletion of `@benchmark A .= A setup=(A=` is broken

[giordano]

On faa6095:

julia> @benchmark A .= A setup=(A=p<TAB>

autocompletes p to primitive type, the only things completed at this point are keywords. This is a regression in Julia v1.12, it works as expected in Julia v1.10. This is similar to #55420, but the condition is quite different.