Remove super-obsolete "dropbox start" autocommand

dotfiles/i3/config

@@ -456,7 +456,6 @@ for_window [class="Orage"]      floating enable
 
 exec "newfeh"
 exec "dunst"
-exec "dropbox start"
 exec "urxvt -e weechat"
 exec "nm-applet"
 exec "blueman-applet"