Replace HTTP link with HTTPS link

This commit replaces an HTTP link in the configuration docs with an
HTTPS link.

docs/reference/setup/configuration.asciidoc

@@ -110,7 +110,7 @@ command line with `es.node.name` or in the config file with `node.name`.
 [[logging]]
 == Logging configuration
 
-Elasticsearch uses http://logging.apache.org/log4j/2.x/[Log4j 2] for
+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, `${sys:es.logs.base_path},
 `${sys:es.logs.cluster_name}`, and `${sys:es.logs.node_name}` (if the node name