Fix return type to allow further security config

Issue gh-10245

Author: dvanbler

config/src/main/java/org/springframework/security/config/annotation/web/configurers/saml2/Saml2LoginConfigurer.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2021 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -128,7 +128,7 @@ public Saml2LoginConfigurer<B> authenticationManager(AuthenticationManager authe
 	 * @param repo the repository of relying parties
 	 * @return the {@link Saml2LoginConfigurer} for further configuration
 	 */
-	public Saml2LoginConfigurer relyingPartyRegistrationRepository(RelyingPartyRegistrationRepository repo) {
+	public Saml2LoginConfigurer<B> relyingPartyRegistrationRepository(RelyingPartyRegistrationRepository repo) {
 		this.relyingPartyRegistrationRepository = repo;
 		return this;
 	}