E-book viewer: Fix copy to clipboard not ignoring text from elements that are marked as non user selectable. Fixes #1991504 [Copy text does not respect user-select: none](https://bugs.launchpad.net/calibre/+bug/1991504)

Apparently the bug in webengine where it does not copy HTML to the
clipbaord is no more, so we can go back to relying on the native copy
which does exclude such text automatically.

src/pyj/read_book/iframe.pyj

@@ -951,12 +951,11 @@ class IframeBoss:
             select_crw(crw)
 
     def copy_selection(self):
-        if not runtime.is_standalone_viewer:
-            try:
-                if document.execCommand('copy'):
-                    return
-            except:
-                pass
+        try:
+            if document.execCommand('copy'):
+                return
+        except:
+            pass
 
         s = window.getSelection()
         text = s.toString()