Hide clipboard side bar button when view only mode

The clipboard side bar button serves no purpose if user uses 'View Only'
mode, this commit hides this button in those instances.

kasmweb/app/ui.js

@@ -1973,6 +1973,8 @@ const UI = {
                 .classList.add('noVNC_hidden');
             document.getElementById('noVNC_mouse_button' + UI.rfb.touchButton)
                 .classList.add('noVNC_hidden');
+            document.getElementById('noVNC_clipboard_button')
+                .classList.add('noVNC_hidden');
         } else {
             document.getElementById('noVNC_keyboard_button')
                 .classList.remove('noVNC_hidden');
@@ -1980,6 +1982,8 @@ const UI = {
                 .classList.remove('noVNC_hidden');
             document.getElementById('noVNC_mouse_button' + UI.rfb.touchButton)
                 .classList.remove('noVNC_hidden');
+            document.getElementById('noVNC_clipboard_button')
+                .classList.remove('noVNC_hidden');
         }
     },