fix(Makefile): update deprecated celery command

[GeekyShacklebolt]

Why was this change necessary?

In the Makefile celery was running with "celery worker -A celeryapp <...>" that is using -A as an option of the worker sub-command. The support for this usage was removed in Celery 5.0.

How does it address the problem?

The updated usage is to use -A as a global option: "celery -A celeryapp worker <...>"

Are there any side effects?

No

References

For Celery v5.1.2:

• Workers guid - https://docs.celeryproject.org/en/v5.1.2/userguide/workers.html
• Daemonization - https://docs.celeryproject.org/en/v5.1.2/userguide/daemonizing.html

[theskumar]

Thank you @GeekyShacklebolt !