Update to Latest rsocket-core

Now that the RSocket Authentication Extension is GA, it's no longer
necessary to override the version locally in the sample.

Issue gh-7935

Author: jzheaux

samples/boot/hellorsocket/spring-security-samples-boot-hellorsocket.gradle

@@ -1,7 +1,5 @@
 apply plugin: 'io.spring.convention.spring-sample-boot'
 
-ext['rsocket.version'] = '1.0.0-RC6'
-
 dependencies {
 	compile project(':spring-security-core')
 	compile project(':spring-security-config')