Fix more missing markup in configuration docs
This commit fixes some missing markup in the configuration docs in the
logging configuration section.
@@ -112,7 +112,7 @@ command line with `es.node.name` or in the config file with `node.name`.
Elasticsearch uses https://logging.apache.org/log4j/2.x/[Log4j 2] for
logging. Log4j 2 can be configured using the log4j2.properties
-file. Elasticsearch exposes three properties, `${sys:es.logs.base_path},
+file. Elasticsearch exposes three properties, `${sys:es.logs.base_path}`,
`${sys:es.logs.cluster_name}`, and `${sys:es.logs.node_name}` (if the node name
is explicitly set via `node.name`) that can be referenced in the configuration
file to determine the location of the log files. The property
