The Plugin's configuration settings are not removed if the plugin is uninstalled. To remove the configuration settings, follow this procedure:

Step 1:

Disable or uninstall the SAML Single Sign on using the Plugin Manager

Step 2: 

Download clearssoconfig-1.2.1.jar and upload it using the Plugin Manager:

Step 3:

Open the URL https://<jira_or_confluence>/plugins/servlet/clearssoconfig

Step 4:

Uninstall the Clear SAML SSO Config plugin