docs: documentation about delete endpoint

[bednar]

Closes #188

Proposed Changes

Added documentation about DeleteApi.

Checklist

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

[codecov]

Codecov Report

Merging #189 (9bd07df) into master (2b7a6c0) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #189   +/-   ##
=======================================
  Coverage   89.82%   89.83%           
=======================================
  Files          26       26           
  Lines        1966     1967    +1     
=======================================
+ Hits         1766     1767    +1     
  Misses        200      200           

Impacted Files	Coverage Δ
influxdb_client/__init__.py	100.00% <100.00%> (ø)

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