remove transaction.status from otel transactions

[SylvainJuge]

What does this PR do?

Removes the transaction.result field value for transactions that are created through the OTel bridge.

When the value is set in the intake protocol, APM server currently keeps the provided value, removing it allows to infer the value from OTel attributes values and stay consistent with native OTLP intake.

Checklist

• This is a bugfix
  • I have updated CHANGELOG.asciidoc
  • I have added tests that would fail without this fix
  • backport changes to Spec + OTel bridge gherkin to upstream APM repo : OTel bridge require null transaction result apm#649

[felixbarny]

LGTM. Does this require changes in the spec?

[ghost]

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• Start Time: 2022-06-02T15:33:23.811+0000

• Duration: 48 min 29 sec

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Test	Results
Failed	0
Passed	2932
Skipped	22
Total	2954

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[github-actions]

/test

[SylvainJuge]

Does this require changes in the spec?

Yes : elastic/apm#649