Remove ForwardDiff trigger

[rsenne]

Removes the AD default in the DynamicPPLExt and trigger. Also, now explicitly pass AutoForwardDiff into the relevant tests

See #52.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.67%. Comparing base (af1aed1) to head (675d89e).

Additional details and impacted files

@@             Coverage Diff             @@
##             main      #55       +/-   ##
===========================================
+ Coverage   82.22%   93.67%   +11.45%     
===========================================
  Files           8        7        -1     
  Lines        1170     1091       -79     
===========================================
+ Hits          962     1022       +60     
+ Misses        208       69      -139     

Flag	Coverage Δ
gpu	94.28% <ø> (?)

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