Fix hash(::MutableTangent) on 32 bit

[oxinabox]

Closes #658

having a UInt64 where I meant UInt broke dispatch and made it ignore the overload for the hash function

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (4a56d9c) 94.15% compared to head (d9304c7) 94.15%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #659   +/-   ##
=======================================
  Coverage   94.15%   94.15%           
=======================================
  Files          15       15           
  Lines         976      976           
=======================================
  Hits          919      919           
  Misses         57       57           

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[gdalle]

Lgtm following https://docs.julialang.org/en/v1/base/base/#Base.hash