Remove nVidia drivers staging PPA link

Remove the link to the nVidia drivers staging PPA, as that PPA is for
other purposes, not really the staging PPA for the driver.
Also, remove call for community testing. Testing is covered by
certification team.

Author: anthonywong

docs/SRU/reference/exception-NVidia-Updates.rst

@@ -170,9 +170,6 @@ QA tests
 -  `Certification test
    suite <https://git.launchpad.net/plainbox-provider-sru/tree/units/sru.pxu>`__
    must pass on a range of hardware.
--  Call for testing is sent to the community via the `community
-   hub <https://community.ubuntu.com>`__ as soon as the drivers are
-   available in the staging PPA.
 
 
 NVidia SRU Template
@@ -246,5 +243,3 @@ References
    drivers <https://nvidia.custhelp.com/app/answers/detail/a_id/3142>`__
 -  `What is a legacy
    GPU <https://www.nvidia.com/object/IO_32667.html>`__
--  `nVidia drivers staging
-   PPA <https://launchpad.net/~canonical-hwe-team/+archive/ubuntu/intermediate-kernel>`__