Add missing `@ConditionalOnClass` check on RedisCacheConfiguration

Closes gh-13508

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/cache/RedisCacheConfiguration.java

@@ -23,6 +23,7 @@ import org.springframework.beans.factory.ObjectProvider;
 import org.springframework.boot.autoconfigure.AutoConfigureAfter;
 import org.springframework.boot.autoconfigure.cache.CacheProperties.Redis;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnBean;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
 import org.springframework.boot.autoconfigure.data.redis.RedisAutoConfiguration;
 import org.springframework.cache.CacheManager;
@@ -45,6 +46,7 @@ import org.springframework.data.redis.serializer.RedisSerializationContext.Seria
  * @since 1.3.0
  */
 @Configuration
+@ConditionalOnClass(RedisConnectionFactory.class)
 @AutoConfigureAfter(RedisAutoConfiguration.class)
 @ConditionalOnBean(RedisConnectionFactory.class)
 @ConditionalOnMissingBean(CacheManager.class)