themes: Update spinner and bgrt diskcrypt dialog

Update the spinner and bgrt themses diskcrypt dialog to match the dialog
from the "Disk decrypt" mockup from:

https://wiki.gnome.org/Design/OS/BootProgress

Signed-off-by: Hans de Goede <hdegoede@redhat.com>

themes/spinner/Makefile.am

@@ -3,7 +3,6 @@ nodist_theme_DATA = spinner.plymouth
 
 dist_theme_DATA =                                                     \
                     background-tile.png                               \
-                    box.png                                           \
                     bullet.png                                        \
                     entry.png                                         \
                     lock.png                                          \