fix 1.10 Vararg deprecation warning

[visr]

Saw this running ArchGDAL tests:

Precompiling project...
  2 dependencies successfully precompiled in 7 seconds. 87 already precompiled.
  1 dependency had warnings during precompilation:
┌ DiskArrays [3c3547ce-8d99-4f5e-a174-61eb10b00ae3]
│  WARNING: Wrapping `Vararg` directly in UnionAll is deprecated (wrap the tuple instead).
│  You may need to write `f(x::Vararg{T})` rather than `f(x::Vararg{<:T})` or `f(x::Vararg{T}) where T` instead of `f(x::Vararg{T} where T)`.
│  WARNING: Wrapping `Vararg` directly in UnionAll is deprecated (wrap the tuple instead).
│  You may need to write `f(x::Vararg{T})` rather than `f(x::Vararg{<:T})` or `f(x::Vararg{T}) where T` instead of `f(x::Vararg{T} where T)`.
│  WARNING: Wrapping `Vararg` directly in UnionAll is deprecated (wrap the tuple instead).
│  You may need to write `f(x::Vararg{T})` rather than `f(x::Vararg{<:T})` or `f(x::Vararg{T}) where T` instead of `f(x::Vararg{T} where T)`.
└

This should still behave the same:

julia> g(x::Vararg{Real}) = 1
g (generic function with 1 method)

julia> g(1.0)
1

julia> g("")
ERROR: MethodError: no method matching g(::String)

Closest candidates are:
  g(::Real...)
   @ Main REPL[11]:1