Update messages/webapp.dev.md

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

Author: deepu-mungamuri94

messages/webapp.dev.md

@@ -100,7 +100,7 @@ Press Ctrl+C to stop.
 
 # info.press-ctrl-c-target
 
-Press Ctrl+C to stop the %s
+Press Ctrl+C to stop the %s.
 
 # info.stopped-target