Adjust chart README.md files to reflect official docs

[programmerq]

The teleport docs use a common template for the teleport user and role to use with the plugin. The README files for the charts differ slightly from the docs. These details can be very important, so it would be great to update these to be in line with those templates.

Here's an example of the differences: (click to expand)

--- README.md-slack	2023-06-27 16:20:22
+++ README.mdx-docs	2023-06-27 16:20:22
@@ -1,23 +1,19 @@
 ---
 kind: role
-version: v6
+version: v5
 metadata:
-  name: teleport-plugin-slack
+  name: access-plugin
 spec:
   allow:
-    logins:
-    - teleport-plugin-slack
     rules:
       - resources: ['access_request']
-        verbs: ['list', 'read', 'update']
-  options:
-    forward_agent: false
-    max_session_ttl: 8760h0m0s
-    port_forwarding: false
+        verbs: ['list', 'read']
+      - resources: ['access_plugin_data']
+        verbs: ['update']
 ---
 kind: user
 version: v2
 metadata:
-  name: teleport-plugin-slack
+  name: access-plugin
 spec:
-  roles: ['teleport-plugin-slack']
+  roles: ['access-plugin']

This template is used by discord, email, mattermost, msteams, and slack: https://github.com/gravitational/teleport/blob/master/docs/pages/includes/plugins/rbac.mdx

This template is used by jira: https://github.com/gravitational/teleport/blob/master/docs/pages/includes/plugins/rbac-update.mdx

https://github.com/gravitational/teleport-plugins/tree/master/charts/access/jira/README.md

https://github.com/gravitational/teleport-plugins/tree/master/charts/access/email/README.md
https://github.com/gravitational/teleport-plugins/tree/master/charts/access/mattermost/README.md
https://github.com/gravitational/teleport-plugins/tree/master/charts/access/pagerduty/README.md
https://github.com/gravitational/teleport-plugins/tree/master/charts/access/slack/README.md

The msteams readme doesn't seem to include this RBAC section.

It would be nice to either update the README.md in each chart to more explicitly endorse the doc site, or at the very least get the information synchronized.