Change tab switching shortcuts to alt-ctrl-left/right

Fixes #5889

core/wiki/config/shortcuts/shortcuts-mac.multids

@@ -1,8 +1,6 @@
 title: $:/config/shortcuts-mac/
 
 bold: meta-B
-input-tab-left: ctrl-Left
-input-tab-right: ctrl-Right
 italic: meta-I
 underline: meta-U
 new-image: ctrl-I

core/wiki/config/shortcuts/shortcuts.multids

@@ -18,8 +18,8 @@ input-accept: Enter
 input-accept-variant: ctrl-Enter
 input-cancel: Escape
 input-down: Down
-input-tab-left: alt-Left
-input-tab-right: alt-Right
+input-tab-left: alt-ctrl-Left
+input-tab-right: alt-ctrl-Right
 input-up: Up
 layout-switcher: ctrl-shift-L
 link: ctrl-L