docs: fix a dead link (operator-framework#1796)

Author: scrocquesel

docs/documentation/features.md

@@ -574,7 +574,7 @@ reconciliations from being triggered when not needed and allowing efficient oper
 [PerResourcePollingEventSource](https://github.com/java-operator-sdk/java-operator-sdk/blob/main/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/polling/PerResourcePollingEventSource.java)
 is used to poll external APIs, which don't support webhooks or other event notifications. It
 extends the abstract
-[CachingEventSource](https://github.com/java-operator-sdk/java-operator-sdk/blob/main/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/CachingEventSource.java)
+[ExternalResourceCachingEventSource](https://github.com/java-operator-sdk/java-operator-sdk/blob/main/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/ExternalResourceCachingEventSource.java)
 to support caching.
 See [MySQL Schema sample](https://github.com/java-operator-sdk/java-operator-sdk/blob/main/sample-operators/mysql-schema/src/main/java/io/javaoperatorsdk/operator/sample/MySQLSchemaReconciler.java)
 for usage.