Deprecate yumpkg.py provider for yum
Force all distros which use yum to use yumpkg5
Remove reference to yumpkg5 in provider override example

yumpkg5 is the default now, so it shouldn't be included in an example of
overriding the provider.
Merge pull request #9129 from terminalmage/deprecate-yumpkg

Deprecate yumpkg in favor of yumpkg5