chore(ci): update default docker image to v2.0.3

[bednar]

Closes #168

Proposed Changes

• Updated default docker image to v2.0.3
• Updated nightly docker image to influxdb2:nightly

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 #179 (0322d5e) into master (5eb4cdf) will increase coverage by 0.25%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #179      +/-   ##
==========================================
+ Coverage   89.47%   89.72%   +0.25%     
==========================================
  Files          26       26              
  Lines        1957     1957              
==========================================
+ Hits         1751     1756       +5     
+ Misses        206      201       -5     

Impacted Files	Coverage Δ
influxdb_client/client/influxdb_client.py	98.44% <0.00%> (+0.77%)	⬆️
influxdb_client/client/delete_api.py	100.00% <0.00%> (+44.44%)	⬆️

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