fix(otlp-http-exporter): remove content length header

[svetlanabrennan]

Signed-off-by: Svetlana Brennan svetlana.svn@gmail.com

Which problem is this PR solving?

OTLP/HTTP and OLTP/PROTO trace exporters are unable to export when gzip compression is used.

Please include a summary of the change and which issue is fixed. Please also include relevant motivation and context. List any dependencies that are required for this change.

Fixes #2876

Short description of the changes

Removed content-length header when gzip is used. Content-length header was setting the uncompressed length which was causing a timeout export issue.

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

Updated existing unit test

Checklist:

• Followed the style guidelines of this project

[codecov]

Codecov Report

Merging #2879 (a38fc31) into main (5d9ed3f) will not change coverage.
The diff coverage is n/a.

❗ Current head a38fc31 differs from pull request most recent head 7f2b72f. Consider uploading reports for the commit 7f2b72f to get more accurate results

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  Misses        366      366           

[Flarna]

CI fails because a changelog entry is needed now (see #2847).