Update Redis example documentation

With the release of Spring-Boot 3.x, the application properties for Redis
changed from `spring.redis` to `spring.data.redis`.
This change will update the documentation to be consistent with the latest
changes in Spring-Boot.

Author: marcel-wollschlaeger

spring-session-docs/modules/ROOT/pages/guides/boot-redis.adoc

@@ -75,9 +75,9 @@ For example, you can include the following in your application.properties:
 ====
 .src/main/resources/application.properties
 ----
-spring.redis.host=localhost # Redis server host.
-spring.redis.password= # Login password of the redis server.
-spring.redis.port=6379 # Redis server port.
+spring.data.redis.host=localhost # Redis server host.
+spring.data.redis.password= # Login password of the redis server.
+spring.data.redis.port=6379 # Redis server port.
 ----
 ====