Update to Spring Security 5.6.3

Closes gh-720

gradle.properties

@@ -3,7 +3,7 @@ org.gradle.jvmargs=-Xmx3g -XX:MaxPermSize=2048m -XX:+HeapDumpOnOutOfMemoryError
 org.gradle.parallel=true
 org.gradle.caching=true
 springFrameworkVersion=5.3.19
-springSecurityVersion=5.5.6
+springSecurityVersion=5.6.3
 springJavaformatVersion=0.0.31
 springJavaformatExcludePackages=org/springframework/security/config org/springframework/security/oauth2
 checkstyleToolVersion=8.34