Fix for ANN memory release bug

[viclafargue]

Answers #3318
This may fix the error observed in CI.

Before the change, the memory manager handler was released first, then the FAISS index.
After the change, the FAISS index is released first, then the memory manager handler is released.

[JohnZed]

Original error not reproducing but there was an error in fetch_20newsgroups (zlib compression error)

[JohnZed]

rerun tests

[codecov-io]

Codecov Report

Merging #3391 (14396bc) into branch-0.18 (550121b) will increase coverage by 0.14%.
The diff coverage is 85.77%.

@@               Coverage Diff               @@
##           branch-0.18    #3391      +/-   ##
===============================================
+ Coverage        71.48%   71.63%   +0.14%     
===============================================
  Files              207      210       +3     
  Lines            16748    16924     +176     
===============================================
+ Hits             11973    12123     +150     
- Misses            4775     4801      +26     

Impacted Files	Coverage Δ
python/cuml/decomposition/incremental_pca.py	94.70% <ø> (ø)
python/cuml/dask/ensemble/base.py	19.69% <30.43%> (+0.36%)	⬆️
python/cuml/ensemble/randomforestregressor.pyx	70.83% <44.44%> (ø)
...ython/cuml/dask/ensemble/randomforestclassifier.py	30.00% <50.00%> (+0.51%)	⬆️
python/cuml/dask/ensemble/randomforestregressor.py	35.08% <50.00%> (+0.54%)	⬆️
python/cuml/fil/fil.pyx	91.87% <60.00%> (-1.88%)	⬇️
python/cuml/ensemble/randomforestclassifier.pyx	73.72% <66.66%> (ø)
python/cuml/multiclass/multiclass.py	84.21% <84.21%> (ø)
python/cuml/model_selection/_split.py	90.35% <90.35%> (ø)
python/cuml/svm/svm_base.pyx	94.27% <91.30%> (-0.63%)	⬇️
... and 17 more

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[JohnZed]

rerun tests

[viclafargue]

rerun tests

[JohnZed]

@gpucibot merge