Throw OverflowError on `copysign(typemin(Int)//1, 1)` (#53395)
The default `copysign(x::Real, y::Real)` in `number.jl` works, so the
incorrect method in `rational.jl` isn't needed.
Here is a benchmark of the new version.
```julia
using BenchmarkTools
function foo!(c,a,b)
c .= copysign.(a, b)
nothing
end
N = 1000
@btime foo!(c,a,b) setup=(c=zeros(Rational{Int},N); a=rand(Int,N).//rand(Int,N); b=fill(-1,N))
```
On master: 406.215 ns (0 allocations: 0 bytes)
On this PR: 869.327 ns (0 allocations: 0 bytes)
