Update messages/webapp.dev.md

Co-authored-by: Juliet Shackell <63259011+jshackell-sfdc@users.noreply.github.com>

Author: deepu-mungamuri94

messages/webapp.dev.md

@@ -116,7 +116,7 @@ proxy server
 
 # info.stop-target-both
 
-dev & proxy servers
+dev and proxy servers
 
 # info.server-running