Better support newer projects install docs

The ops:docs-install-guide tag as currently written does not allow a project
which has made a guide using source, rather than packages, to attain the tag.

This a particular problem for new projects and creates a catch-22 situation
where distros are only likely to package more 'mature'/'adopted' projects,
but users might only adopt a project if there's an install guide.

This change removes the references to package management systems while keeping
the need for installation guides to support installation (whether it be source,
packages, or some other method) on the multiple distros required to make a
project installable to the majority of OpenStack users.

Change-Id: I939ea9643e9d609f2ab6592fd68e0b735f53f252
Co-Authored-By: Mike Perez <thingee@gmail.com>

descriptions/ops-docs-install-guide.rst

@@ -43,8 +43,8 @@ Tag application process
   present for some time afterward. Reasonable efforts should be made to
   take this into account, with the focus always on providing the most
   information to the operator
-- the application of this tag follows the three-package-management-system
-  classification used by the documentation team (apt, yum, zypper) for their
+- the application of this tag follows the distro classifications used by the
+  documentation team (SUSE, RHEL/CentOS, Ubuntu) for their
   supported releases: the aim is a general guide to the existence of
   documentation - not an exhaustive distro-by-distro breakdown. Where there
   are differences between distributions or versions significant enough they
@@ -86,7 +86,7 @@ Attributes
 ==========
 
 - status    - the tag application status
-- bug_link  - URL(s) to major bugs afflicting a project's packages
+- bug_link  - URL(s) to major bugs afflicting a project's install
 - description - optional details regarding the tag application
 - caveats   - Any exceptions to the general status. Follows the same
               attributes as the general status, in addition to a 'label'