Use Spring Security 6 for every sample

gradle.properties

@@ -1,5 +1,4 @@
 version=6.0.0-SNAPSHOT
-spring-security.version=6.0.0-SNAPSHOT
 org.gradle.jvmargs=-Xmx3g -XX:+HeapDumpOnOutOfMemoryError
 org.gradle.parallel=true
 org.gradle.caching=true