Fix deprecated numpy data type usage in bilinear resampling

[danschef]

This fixes a DeprecationWarning coming from numpy:

/root/mambaforge/envs/ci_env/lib/python3.10/site-packages/pyresample/bilinear/_base.py:220
`np.float` is a deprecated alias for the builtin `float`. To silence this warning, use `float` by itself. Doing this will not modify any behavior and is safe. If you specifically wanted the numpy scalar type, use `np.float64` here. Deprecated in NumPy 1.20; for more details and guidance: https://numpy.org/devdocs/release/1.20.0-notes.html#deprecations

• Closes #xxxx
• Tests added
• Tests passed
• Passes git diff origin/main **/*py | flake8 --diff
• Fully documented

[codecov]

Codecov Report

Merging #399 (33d09be) into main (e6a452e) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main     #399   +/-   ##
=======================================
  Coverage   93.81%   93.81%           
=======================================
  Files          65       65           
  Lines       11076    11076           
=======================================
  Hits        10391    10391           
  Misses        685      685           

Flag	Coverage Δ
unittests	93.81% <100.00%> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
pyresample/bilinear/_base.py	95.69% <100.00%> (ø)

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[coveralls]

Coverage remained the same at 93.619% when pulling 33d09be on danschef:main into e6a452e on pytroll:main.

[djhoese]

Looks good to me. Thank you.