delete useless "not implemented" methods

[nsajko]

Help the compiler and enable more useful error messages for users.

[0x0f0f0f]

cc @shashi

[ChrisRackauckas]

Yes accept this. It's a violation of our coding standards to not appropriately hit missing dispatch errors since then it doesn't recover properly in contexts like AD

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 47.36%. Comparing base (b5c0ceb) to head (ca2bf93).
Report is 28 commits behind head on master.

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Additional details and impacted files

@@            Coverage Diff             @@
##           master      #34      +/-   ##
==========================================
+ Coverage   42.85%   47.36%   +4.51%     
==========================================
  Files           3        3              
  Lines          28       19       -9     
==========================================
- Hits           12        9       -3     
+ Misses         16       10       -6     

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