InfoPanel: indicate lack of support for duotone weight in JS lib

While phosphor-icons uses an icon font implementation, we won't be able
to provide the duotone weight in that library. We now indicate lack of
support by disabling the code snippet and copy button.

src/components/IconGrid/IconGrid.css

@@ -121,6 +121,10 @@
   cursor: pointer;
 }
 
+.snippet button:disabled {
+  cursor: not-allowed;
+}
+
 .button-row {
   display: flex;
 }