fix: cannot use community-general version 12 - no py27 and py36 support

community.general version 12 has dropped support for py27 and py36 - ensure that
the roles do not install/use this version - see
https://github.com/ansible-collections/community.general/issues/582

By default, installation will get the latest 11.x version. The lower bound
`6.6.0` is an older version, but I don't want to restrict the ability of a user
of a particular role to use an old version, rather than forcing them to use
`11.x` or later. Some roles like `rhc` explicitly require `6.6.0` or later - I
think this is a reasonable lower bound for all roles.If a role needs a different
version, the role can define its own `community_general_version` in the role's
`host_vars` file in .github.

Standardize file format across all roles for consistency and ease of updating

This update may remove the SPDX license information from the file - this is ok -
the role/project already has a license, this file is trivial, and many
requirements files do not have the license header anyway.

Signed-off-by: Rich Megginson <rmeggins@redhat.com>

meta/collection-requirements.yml

@@ -1,3 +1,4 @@
+# DO NOT EDIT THIS FILE - managed by linux-system-roles/.github
 ---
 collections:
   - name: ansible.posix