Delete shortcuts.md

The in-app keyboard shortcuts view has more.
https://github.com/matrix-org/matrix-react-sdk/pull/4231

docs/shortcuts.md

@@ -1,15 +0,0 @@
-# Keyboard Shortcuts
-
-The modifier is <kbd>Ctrl</kbd> on Windows & Linux and <kbd>⌘</kbd> on Mac.
-
-- <kbd>Ctrl</kbd>/<kbd>⌘</kbd>+<kbd>m</kbd> - toggle markdown
-- <kbd>Ctrl</kbd>/<kbd>⌘</kbd>+<kbd>d</kbd> - toggle mic mute
-- <kbd>Ctrl</kbd>/<kbd>⌘</kbd>+<kbd>e</kbd> - toggle video on/off
-- <kbd>Ctrl</kbd>/<kbd>⌘</kbd>+<kbd>k</kbd> - jump to named room
-- <kbd>↑</kbd>/<kbd>↓</kbd> - navigate old messages to edit when the composer is in focus
-- <kbd>↑</kbd>/<kbd>↓</kbd> - next/prev room when focus in room list
-- <kbd>Alt</kbd>+<kbd>↑</kbd>/<kbd>↓</kbd> - resend previous messages when the composer is in focus
-- <kbd>PageUp</kbd>/<kbd>PageDown</kbd> - scroll timeline up/down
-- <kbd>Ctrl</kbd>/<kbd>⌘</kbd>+<kbd>Home</kbd>/<kbd>End</kbd> - jump to
-  start/end of the composer when focused, otherwise jump to timeline start/end
-- <kbd>Ctrl</kbd>/<kbd>⌘</kbd>+<kbd>`</kbd> - toggle the top left menu