fix: serialize numpy floats

[bednar]

Closes #252

Proposed Changes

Fixed serializing numpy float types into Line Protocol.

• https://numpy.org/doc/stable/reference/arrays.scalars.html#floating-point-types

Checklist

• CHANGELOG.md updated
• Rebased/mergeable
• A test has been added if appropriate
• pytest tests completes successfully
• Commit messages are in semantic format
• Sign CLA (if not already signed)

[codecov-commenter]

Codecov Report

Merging #254 (0e6978a) into master (bccc2b8) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #254   +/-   ##
=======================================
  Coverage   91.93%   91.93%           
=======================================
  Files          25       25           
  Lines        2033     2033           
=======================================
  Hits         1869     1869           
  Misses        164      164           

Impacted Files	Coverage Δ
...fluxdb_client/client/write/dataframe_serializer.py	98.66% <100.00%> (ø)

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