Fix usage of MLJModelInterface

[davnn]

The current usage of MLJModelInterface in the affected functions requires a global MLJModelInterface to be available, e.g. only importing @mlj_model would fail when MLJModelInterface is not available.

Using $MLJModelInterface fixes the problem by referring to the local MLJModelInterface.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (9736531) 89.26% compared to head (33c6f60) 89.26%.

Additional details and impacted files

@@           Coverage Diff           @@
##              dev     #184   +/-   ##
=======================================
  Coverage   89.26%   89.26%           
=======================================
  Files           8        8           
  Lines         382      382           
=======================================
  Hits          341      341           
  Misses         41       41           

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[davnn]

@ablaom OutlierDetectionInterface.jl depends on @mlj_model, but cannot guarantee that MLJModelInterface is always available globally. Disregarding the problem for OutlierDetection.jl, this probably represents a bug for all users not importing the entire package.

[ablaom]

Looks good to me.