meta/classes-global: remove package_tar.bbclass

Remove package_tar.bbclass, which is no longer in use in oe-core
and meta-oe, and which the document reports as broken and unsupported.

Signed-off-by: Michael Opdenacker <michael.opdenacker@bootlin.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>