Remove unused importlib-metadata dependency

[eleanorRumsey]

Hey! We're using this package here at Fellow, but there's a dependency conflict in importlib-metadata with another package (opentelemetry-api). It doesn't seem like importlib-metadata is actually used anywhere here, would it be possible to remove it?

celery-heimdall/pyproject.toml

Line 17 in b6709f6

importlib-metadata = "<=4.13"

[TkTech]

Hi! This was to work around this specific issue: python/importlib_metadata#411, which universally broke importing celery. Since this is no longer needed, the pin can be removed. I'll push 1.0.1 shortly.