Move scratchpad bindings to grave/tilde

Too often, minus got confused with 0.

dotfiles/i3/config

@@ -121,8 +121,8 @@ bindsym $mod+Shift+8 move container to workspace $w8
 bindsym $mod+Shift+9 move container to workspace $w9
 bindsym $mod+Shift+0 move container to workspace $w0
 
-bindsym $mod+Shift+minus move scratchpad
-bindsym $mod+minus scratchpad show
+bindsym $mod+Shift+grave move scratchpad
+bindsym $mod+grave scratchpad show
 
 # mark mode
 bindsym $mod+equal               mode "mark"