Quota configuration: improve example oslo_limit section

This patch:
- uses "glance" instead of "MY_SERVICE";
- uses the already existing public glance endpoint id rather than
  "ENDPOINT_ID";
- uses the already existing "GLANCE_PASS" rather than introducing
  "MY_PASSWORD".

Closes-Bug: #1990854
Change-Id: I8f5214b879818ec5f1a62d369274ad0d67396b9b

doc/source/install/configure-quotas.rst

@@ -6,20 +6,23 @@
      auth_url = http://controller:5000
      auth_type = password
      user_domain_id = default
-     username = MY_SERVICE
+     username = glance
      system_scope = all
-     password = MY_PASSWORD
-     endpoint_id = ENDPOINT_ID
+     password = GLANCE_PASS
+     endpoint_id = 340be3625e9b4239a6415d034e98aace
      region_name = RegionOne
 
   .. end
 
-  Make sure that the MY_SERVICE account has reader access to
+  Replace ``GLANCE_PASS`` with the password you chose for the
+  ``glance`` user in the Identity service.
+
+  Make sure that the glance account has reader access to
   system-scope resources (like limits):
 
   .. code-block:: console
 
-     $ openstack role add --user MY_SERVICE --user-domain Default --system all reader
+     $ openstack role add --user glance --user-domain Default --system all reader
 
   .. end