Move security.* to spring.security.*

This commit also removes `security.basic.enabled` as this property is
no longer required.

Closes gh-10296

spring-boot-samples/spring-boot-sample-secure-oauth2-resource/src/main/resources/application.properties

@@ -1,6 +1,5 @@
 server.port=8081
 spring.datasource.platform=h2
-security.basic.enabled=false
 security.oauth2.resource.id=service
 security.oauth2.resource.userInfoUri=http://localhost:8080/user
 logging.level.org.springframework.security=DEBUG