Fix WebSessionReactiveSecurityRepository Supports Cache

Fix the checkstyle for this feature

Closes gh-8422

Author: rwinch

web/src/main/java/org/springframework/security/web/server/context/WebSessionServerSecurityContextRepository.java

@@ -91,7 +91,7 @@ public Mono<SecurityContext> load(ServerWebExchange exchange) {
 					: LogMessage.format("No SecurityContext found in WebSession: '%s'", session));
 			return Mono.justOrEmpty(context);
 		});
-		return (cacheSecurityContext) ? result.cache() : result;
+		return (this.cacheSecurityContext) ? result.cache() : result;
 	}
 
 }