docs: remove outdated keyboard shortcut for note block creation (#7803)

The Keyboard Shortcuts dialog documented "d,r,m,f,s,l,t" as typing
these letters to create do/re/mi/fa/sol/la/ti note blocks. No
keydown handler in keyboard-controller.js (or anywhere else in the
codebase) implements this behavior, so the entry has been
misleading users since it was carried over from an old, unrelated
help card in #6346.

Remove the stale entry so the dialog matches actual application
behavior. No keyboard handling logic is touched.

Signed-off-by: Vanshika <pahalvanshikaa@gmail.com>

Author: vanshika2720

js/activity.js

@@ -3591,12 +3591,6 @@ class Activity {
                         {
                             keys: platformKeys("Esc", "Esc"),
                             action: _("Hide block search when it is open")
-                        },
-                        {
-                            keys: platformKeys("d,r,m,f,s,l,t", "d,r,m,f,s,l,t"),
-                            action: _(
-                                "You can type d to create a do block and r to create a re block etc."
-                            )
                         }
                     ]
                 },