chore(propagation): remove b3 single header

[mabdinur]

Blocked by: DataDog/system-tests#3943

Checklist

• PR author has checked that all the criteria below are met
• The PR description includes an overview of the change
• The PR description articulates the motivation for the change
• The change includes tests OR the PR description describes a testing strategy
• The PR description notes risks associated with the change, if any
• Newly-added code is easy to change
• The change follows the library release note guidelines
• The change includes or references documentation updates if necessary
• Backport labels are set (if applicable)

Reviewer Checklist

• Reviewer has checked that all the criteria below are met
• Title is accurate
• All changes are related to the pull request's stated goal
• Avoids breaking API changes
• Testing strategy adequately addresses listed risks
• Newly-added code is easy to change
• Release note makes sense to a user of the library
• If necessary, author has acknowledged and discussed the performance implications of this PR as reported in the benchmarks PR comment
• Backport labels are set in a manner that is consistent with the release branch maintenance policy

[github-actions]

CODEOWNERS have been resolved as:

releasenotes/notes/remove-b3-single--4c16c32466c69709.yaml              @DataDog/apm-python
ddtrace/propagation/http.py                                             @DataDog/apm-sdk-api-python
ddtrace/settings/_config.py                                             @DataDog/apm-core-python
docs/configuration.rst                                                  @DataDog/python-guild
tests/tracer/test_global_config.py                                      @DataDog/apm-sdk-api-python
tests/tracer/test_propagation.py                                        @DataDog/apm-sdk-api-python

[pr-commenter]

Benchmarks

Benchmark execution time: 2025-02-03 15:55:43

Comparing candidate commit 5fbd839 in PR branch munir/remove-b3-single-headers with baseline commit a22143d in branch 3.x-staging.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 394 metrics, 2 unstable metrics.

[ZStriker19]

Shouldn’t we remove it from http.py and also tests/tracer/test_propagation.py?

[datadog-dd-trace-py-rkomorn]

Datadog Report

Branch report: munir/remove-b3-single-headers
Commit report: 5fbd839
Test service: dd-trace-py

✅ 0 Failed, 130 Passed, 1378 Skipped, 4m 18.74s Total duration (35m 11.91s time saved)