This setting is the default one for the Role Manager and is the same in all Sitefinity versions. When the roleManager is set to false, this means that the installation wizard needs to start because it assumes Sitefinity is not yet installed. Once you install Sitefinity, the setting automatically changes to "true".
When upgrading Sitefinity, you need to disregard this setting in the new web.config and leave the value to "true".
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