fix: Remove Content-Encoding=Identity as the header as it violates the RFC

[tj---]

Closes open-telemetry/opentelemetry-collector#8114

Proposed Changes

Content-Encoding: identity is incorrect and must not be set. As a result, the client is failing to write metrics to the OpenTelemetry Collector v0.81.0
RFC snippet: open-telemetry/opentelemetry-collector#8114 (comment)

This change removes the hardcoded Content-Encoding: identity so that the remote servers don't reject the request. The go library of influx-client also does not add this header.

Checklist

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

[bednar]

@tj--- thanks for your PR 👍

Can you please satisfy our checklist, after that we will merge this PR:

[codecov-commenter]

Codecov Report

Patch and project coverage have no change.

Comparison is base (992ff7c) 90.30% compared to head (53b3594) 90.30%.

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Additional details and impacted files

@@           Coverage Diff           @@
##           master     #595   +/-   ##
=======================================
  Coverage   90.30%   90.30%           
=======================================
  Files          39       39           
  Lines        3456     3456           
=======================================
  Hits         3121     3121           
  Misses        335      335           

Impacted Files	Coverage Δ
influxdb_client/client/write_api.py	97.30% <ø> (ø)
influxdb_client/client/write_api_async.py	100.00% <ø> (ø)

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[tj---]

Can you please satisfy our checklist, after that we will merge this PR:

@bednar Sorry, I may have messed up the commit messages. But the rest of the points should be in place now.

[bednar]

@tj--- thanks again for your PR 👍

LGTM 🚀