Update to Spring Security 5.8.15

Closes gh-962

Author: jzheaux

dependencies/build.gradle

@@ -66,9 +66,9 @@ dependencies {
 		api "org.slf4j:jcl-over-slf4j:1.7.36"
 		api "org.slf4j:log4j-over-slf4j:1.7.36"
 		api "org.slf4j:slf4j-api:1.7.36"
-		api "org.springframework.security:spring-security-config:5.6.5"
-		api "org.springframework.security:spring-security-core:5.6.5"
-		api "org.springframework.security:spring-security-ldap:5.6.5"
+		api "org.springframework.security:spring-security-config:5.8.15"
+		api "org.springframework.security:spring-security-core:5.8.15"
+		api "org.springframework.security:spring-security-ldap:5.8.15"
 		api "org.slf4j:slf4j-log4j12:1.7.36"
 		api "org.springframework.ldap:spring-ldap-core:2.3.4.RELEASE"
 	}