Fix: Vararg{<:AbstractFloat} -> Vararg{AbstractFloat}

[devmotion]

Fixes https://github.com/EnzymeAD/Enzyme.jl/actions/runs/19623837183/job/56188979383#step:12:218:

┌ Enzyme
│  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)`.
│  To make this warning an error, and hence obtain a stack trace, use `julia --depwarn=error`.
└

[wsmoses]

oh thats where it's been coming from?

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 67.81%. Comparing base (f9dd728) to head (7a41503).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2809      +/-   ##
==========================================
- Coverage   67.81%   67.81%   -0.01%     
==========================================
  Files          58       58              
  Lines       20717    20717              
==========================================
- Hits        14050    14049       -1     
- Misses       6667     6668       +1     

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[devmotion]

Yes. CI seems to confirm it, I can't see these warnings in the logs anymore.