chore: bump celery from 4.4.7 to 5.2.6 in /worker

Bumps [celery](https://github.com/celery/celery) from 4.4.7 to 5.2.6.
- [Release notes](https://github.com/celery/celery/releases)
- [Changelog](https://github.com/celery/celery/blob/v5.2.6/Changelog.rst)
- [Commits](celery/celery@v4.4.7...v5.2.6)

---
updated-dependencies:
- dependency-name: celery
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

worker/requirements.txt

@@ -1,6 +1,6 @@
 # This file is auto-generated by tools/extract-requirements.sh.
 # Please do not edit this file, edit the setup.py file!
-celery==4.4.7
+celery==5.2.6
 kombu==4.6.10
 mutagen>=1.31.0
 requests>=2.7.0

worker/setup.py

@@ -22,7 +22,7 @@
     packages=["libretime_worker"],
     python_requires=">=3.6",
     install_requires=[
-        "celery==4.4.7",
+        "celery==5.2.6",
         "kombu==4.6.10",
         "mutagen>=1.31.0",
         "requests>=2.7.0",