Need to drop code paths specific to Python 3.7, 3.8, 3.9 once we stop supporting those versions

[vchudnov-g]

When we drop support for Python 3.7 and 3.8, we need to drop support for code paths intended solely for those Python versions. Such code paths should ideally be marked by referencing this issue in a TODO, but to be conscientious we should also grep for the strings "3.7" and "3.8".

[parthea]

Also added 3.9 to this bug as importlib.metadata.packages_distributions() is only supported in Python 3.10+
https://docs.python.org/3/library/importlib.metadata.html#package-distributions

python-api-core/google/api_core/_python_version_support.py

Lines 156 to 169 in 6493118

	if sys.version_info < (3, 8):
	def _get_pypi_package_name(module_name): # pragma: NO COVER
	"""Determine the PyPI package name for a given module name."""
	return None
	else:
	from importlib import metadata
	def _get_pypi_package_name(module_name):
	"""Determine the PyPI package name for a given module name."""
	try:
	# Get the mapping of modules to distributions
	module_to_distributions = metadata.packages_distributions()