fix: data types for querying into DataFrame

[bednar]

Closes #379

Proposed Changes

Fixed Pandas DataFrame's type.

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 #380 (212b784) into master (554e8a0) will increase coverage by 0.04%.
The diff coverage is 100.00%.

❗ Current head 212b784 differs from pull request most recent head a2ccc4d. Consider uploading reports for the commit a2ccc4d to get more accurate results

@@            Coverage Diff             @@
##           master     #380      +/-   ##
==========================================
+ Coverage   92.90%   92.94%   +0.04%     
==========================================
  Files          28       28              
  Lines        2395     2395              
==========================================
+ Hits         2225     2226       +1     
+ Misses        170      169       -1     

Impacted Files	Coverage Δ
influxdb_client/client/flux_csv_parser.py	97.98% <100.00%> (+0.50%)	⬆️

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