Remove dead pkg_resources fallback

[junagent]

Summary

Simplify pipeline/__init__.py by removing the dead pkg_resources fallback chain.

Problem

The file had 24 lines of complex fallback logic:

PackageNotFoundError = None
DistributionNotFound = None
try:
    from importlib.metadata import PackageNotFoundError
    from importlib.metadata import version as get_version
except ImportError:
    get_version = None
    PackageNotFoundError = None
if get_version is None:
    try:
        from pkg_resources import DistributionNotFound, get_distribution
        def get_version(x):
            return get_distribution(x).version
    except ImportError:
        get_version = None
        DistributionNotFound = None
        get_distribution = None

__version__ = None
if get_version is not None:
    try:
        __version__ = get_version("django-pipeline")
    except PackageNotFoundError:
        pass
    except DistributionNotFound:
        pass

Since django-pipeline requires Python >=3.9 (per pyproject.toml), importlib.metadata is always available. The entire pkg_resources fallback and ImportError handling is dead code.

Fix

Replace with 5 lines:

from importlib.metadata import PackageNotFoundError, version

try:
    __version__ = version("django-pipeline")
except PackageNotFoundError:
    __version__ = None

• 19 lines of dead code removed
• Uses stdlib importlib.metadata directly (no fallbacks needed)
• Same behavior for Python 3.9+