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

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

webapp/platform/types/src/config.ts

@@ -776,7 +776,6 @@ export type ExperimentalSettings = {
     ClientSideCertCheck: string;
     LinkMetadataTimeoutMilliseconds: number;
     RestrictSystemAdmin: boolean;
-    UseNewSAMLLibrary: boolean;
     EnableSharedChannels: boolean;
     EnableRemoteClusterService: boolean;
     DisableAppBar: boolean;