classes/pypi: update the default UPSTREAM_CHECK_URI to use the simple repo API

classes/pypi: update the default UPSTREAM_CHECK_URI to use the simple repo API

Update the UPSTREAM_CHECK_URI to leverage the simple repo API.  The
project URLs require javascript which breaks the version checking fetch
and subsequent logic.  The simple repo API provides similar
functionality with a well defined spec which is used by tools such as
pip.  Also update the UPSTREAM_CHECK_REGEX to be compatible with the
information retrieved via the API

Signed-off-by: Derek Straka <derek@asterius.io>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>