Fix scipy factorized import

[A-CGray]

Purpose

SciPy has started producing the following deprecation warnings when running pyGeo:

DeprecationWarning: Please use `factorized` from the `scipy.sparse.linalg` namespace, the `scipy.sparse.linalg.eigen` namespace is deprecated.

This PR updates where we get the factorized function from to fix this. I checked, and the factorized function is available in the new location in scipy 1.5.4 which is the oldest version we currently we support.

Exactly the same as mdolab/pyspline#53

Expected time until merged

1 day

Type of change

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (non-backwards-compatible fix or feature)
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no API changes)
• Documentation update
• Maintenance update
• Other (please describe)

Testing

Checklist

• I have run flake8 and black to make sure the Python code adheres to PEP-8 and is consistently formatted
• I have formatted the Fortran code with fprettify or C/C++ code with clang-format as applicable
• I have run unit and regression tests which pass locally with my changes
• I have added new tests that prove my fix is effective or that my feature works
• I have added necessary documentation

[sseraj]

Can you also fix this is pyBlock.fitGlobal ?

[codecov]

Codecov Report

Merging #185 (87dd700) into main (8e6ba8a) will not change coverage.
The diff coverage is 50.00%.

@@           Coverage Diff           @@
##             main     #185   +/-   ##
=======================================
  Coverage   64.76%   64.76%           
=======================================
  Files          47       47           
  Lines       11949    11949           
=======================================
  Hits         7739     7739           
  Misses       4210     4210           

Impacted Files	Coverage Δ
pygeo/pyBlock.py	47.87% <0.00%> (ø)
pygeo/pyGeo.py	39.71% <100.00%> (ø)

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