Show DeprecationWarning when Sklearn Ensemblers are called

[christopherbunn]

When a sklearn ensembler is instantiated, show a warning that it will removed in the next release.

[codecov]

Codecov Report

Merging #2859 (013d7ea) into main (7353fa6) will increase coverage by 0.1%.
The diff coverage is 100.0%.

@@           Coverage Diff           @@
##            main   #2859     +/-   ##
=======================================
+ Coverage   99.8%   99.8%   +0.1%     
=======================================
  Files        305     305             
  Lines      28353   28373     +20     
=======================================
+ Hits       28272   28292     +20     
  Misses        81      81             

Impacted Files	Coverage Δ
...mponents/ensemble/sklearn_stacked_ensemble_base.py	100.0% <100.0%> (ø)
..._tests/test_sklearn_stacked_ensemble_classifier.py	100.0% <100.0%> (ø)
...t_tests/test_sklearn_stacked_ensemble_regressor.py	100.0% <100.0%> (ø)

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[angela97lin]

LGTM, thanks! Just left a comment about the test name 😅

[angela97lin]

Test name might be wrong? 😂