Update docs/index.asciidoc

Co-authored-by: Rob Bavey <[email protected]>

Author: mashhurs

docs/index.asciidoc

@@ -503,7 +503,7 @@ A password when using HTTP Basic Authentication to connect to {es}.
 
 Address of the HTTP forward proxy used to connect to the {es} cluster.
 An empty string is treated as if proxy was not set.
-It is useful when using environment variables e.g. `proxy => '${LS_PROXY:}'`.
+Environment variables may be used to set this value,  e.g. `proxy => '${LS_PROXY:}'`.
 
 [id="plugins-{type}s-{plugin}-ssl_certificate"]
 ===== `ssl_certificate`