chore(sinks)!: remove deprecated headers option from http and opentelemetry sinks

[thomasqueirozb]

Summary

Removes the headers top-level option from the http and opentelemetry sinks. This option has been deprecated since v0.33.0 in favor of request.headers.

Vector configuration

NA

How did you test this PR?

NA

Change Type

• Bug fix
• New feature
• Dependencies
• Non-functional (chore, refactoring, docs)
• Performance

Is this a breaking change?

• Yes
• No

Does this PR include user facing changes?

• Yes. Please add a changelog fragment based on our guidelines.
• No. A maintainer will apply the no-changelog label to this PR.

References

NA

[datadog-vectordotdev]

⚠️ Tests

✨ Fix all issues with Cursor

⚠️ Warnings

🧪 1 Test failed

sources::file::tests::file_start_position_server_restart_unfinalized from vector     (Fix with Cursor)

Test has failed

ℹ️ Info

No other issues found (see more)

❄️ No new flaky tests detected

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