Upgrade to Spring Security 5.1.6

Closes gh-17794

Author: snicoll

spring-boot-project/spring-boot-dependencies/pom.xml

@@ -175,7 +175,7 @@
 		<spring-plugin.version>1.2.0.RELEASE</spring-plugin.version>
 		<spring-restdocs.version>2.0.3.RELEASE</spring-restdocs.version>
 		<spring-retry.version>1.2.4.RELEASE</spring-retry.version>
-		<spring-security.version>5.1.5.RELEASE</spring-security.version>
+		<spring-security.version>5.1.6.RELEASE</spring-security.version>
 		<spring-session-bom.version>Bean-SR7</spring-session-bom.version>
 		<spring-ws.version>3.0.7.RELEASE</spring-ws.version>
 		<sqlite-jdbc.version>3.25.2</sqlite-jdbc.version>