Add missing option `Read-Only Editor` to auto_assign_org_role description (#5139)

Commit adds missing option `Read-Only Editor` to `auto_assign_org_role` description.

docs/sources/installation/configuration.md

@@ -226,7 +226,7 @@ organization to be created for that new user.
 
 
 The role new users will be assigned for the main organization (if the
 The role new users will be assigned for the main organization (if the
 above setting is set to true).  Defaults to `Viewer`, other valid
 above setting is set to true).  Defaults to `Viewer`, other valid
-options are `Admin` and `Editor`.
+options are `Admin` and `Editor` and `Read-Only Editor`.
 
 
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