Warning when running PR tests: wrapping `Vararg` directly in UnionAll is deprecated

The following warning is generated:
```
┌ BeamTracking
│  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)`.
└  
```