Update README.md

Author: mpucholblasco

README.md

@@ -72,4 +72,4 @@ Flags:
 * `logstash_node_queue_page_capacity_bytes`: queue_page_capacity_bytes (counter)
 
 ## Integration tests
-In order to execute manual integration tests (to know if certain logstash version is compatible with logstash-exporter), you can follow instructions present on file [](integration-tests/README.md).
+In order to execute manual integration tests (to know if certain logstash version is compatible with logstash-exporter), you can follow instructions present on file [integration-tests/README.md](integration-tests/README.md).