Roundup Tracker isssue #: 2550857

Remove pair of single quotes that breaks the "Provisional User"
customization example.

Author: rouilj

doc/customizing.txt

@@ -4755,8 +4755,8 @@ users, replacing the existing ``'User'`` values::
 
     [main]
     ...
-    new_web_user_roles = 'Provisional User'
-    new_email_user_roles = 'Provisional User'
+    new_web_user_roles = Provisional User
+    new_email_user_roles = Provisional User
 
 
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