Update dependency org.springframework.security:spring-security-cas to v6

Author: renovate[bot]

gradle.properties

@@ -3,7 +3,7 @@ projectVersion=4.0.0
 threeZeroXProjectVersion=3.0.1
 casClientCoreVersion=3.6.4
 springSecurityCoreVersion=5.3.0
-springSecurityVersion=5.8.9
+springSecurityVersion=6.2.1
 javaxServletApiVersion=4.0.1
 assetPipelineVersion=3.4.7
 projectDesc=The CAS plugin adds CAS single sign-on support to a Grails application that uses Spring Security.