fix(tutorials.js): improve error message when encoding cannot be rend…

…ered

As mentioned by @KristinaRichts and @krHERO ,
the current error message when an encoding cannot be rendered in the tutorials
was misleading ("Please adjust your encoding …").

js/mei-tutorials.js

@@ -425,7 +425,7 @@ function renderVerovio(validationString) {
 
     if (error) {
         // display message
-        document.getElementById('rendering').innerHTML = 'please adjust encoding to enable rendering';
+        document.getElementById('rendering').innerHTML = 'The current encoding cannot be rendered.';
     } else {
         // display svg
         document.getElementById('rendering').innerHTML = svg;