[MM-57085] Remove UseNewSAMLLibrary experimental setting (#26392)

Co-authored-by: Mattermost Build <build@mattermost.com>

e2e-tests/cypress/tests/support/api/on_prem_default_config.json

@@ -484,7 +484,6 @@
         "ClientSideCertCheck": "secondary",
         "LinkMetadataTimeoutMilliseconds": 5000,
         "RestrictSystemAdmin": false,
-        "UseNewSAMLLibrary": false,
         "EnableSharedChannels": false,
         "EnableRemoteClusterService": false,
         "DisableAppBar": false,