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

spring-boot-samples/spring-boot-sample-web-secure-custom/src/main/resources/application.properties

@@ -1,3 +1,2 @@
 spring.thymeleaf.cache: false
-security.basic.enabled: false
 logging.level.org.springframework.security: INFO

spring-boot-samples/spring-boot-sample-web-secure-jdbc/src/main/resources/application.properties

@@ -1,4 +1,3 @@
 debug: true
 spring.thymeleaf.cache: false
-security.basic.enabled: false
 logging.level.org.springframework.security: INFO

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

@@ -1,5 +1,4 @@
 spring.thymeleaf.cache: false
-security.basic.enabled: false
 # demo only:
 logging.level.org.springframework.security: INFO
 logging.level.org.springframework.boot.actuate.audit.listener.AuditListener: DEBUG