Update error msgs for button-states.html (#160)

Minor changes to the error msgs for 500 ad 503 errors.

Author: Anna-Sutton

app/views/button-states.html

@@ -92,15 +92,15 @@ <h2 class="nhsuk-heading-m">Example showing server down (503)</h2>
         }
 
         document.getElementById('button-server-error-example').addEventListener('click', function(event) {
-          setButtonAsSaving(event.target, "Save failed due to server error. Try again.")
+          setButtonAsSaving(event.target, "Save failed because of a server error. Try again.")
         })
 
         document.getElementById('button-timeout-example').addEventListener('click', function(event) {
           setButtonAsSaving(event.target, "Save failed. Check your internet connection and try again.")
         })
 
         document.getElementById('button-server-down-example').addEventListener('click', function(event) {
-          setButtonAsSaving(event.target, "Save failed because of server error. Try again.")
+          setButtonAsSaving(event.target, "Save failed because the server is temporarily unavailable. Try again.")
         })
 
       </script>