Use alternatives pointing to "kali-theme" and not "active-theme"

The path with "active-theme" are already "managed" by desktop-base
and we don't want an install+removal of desktop-base to mess with the
alternatives that we have setup in kali-desktop-base.

Restore the removal code for alternatives that were voluntarily shared
with desktop-base.

debian/kali-desktop-base.postinst

@@ -36,23 +36,23 @@ if [ "$1" = "configure" ] || [ "$1" = "abort-upgrade" ] || [ "$1" = "abort-remov
     # (for GNOME)
     update-alternatives --install \
 	/usr/share/images/desktop-base/desktop-background.xml \
-	desktop-background.xml /usr/share/desktop-base/active-theme/wallpaper/gnome-background.xml 210
+	desktop-background.xml /usr/share/desktop-base/kali-theme/wallpaper/gnome-background.xml 210
 
     # Set up an alternative for the XML version of the lock screen
     # (for GNOME)
     update-alternatives --install \
 	/usr/share/images/desktop-base/desktop-lockscreen.xml \
-	desktop-lockscreen.xml /usr/share/desktop-base/active-theme/lockscreen/gnome-background.xml 210
+	desktop-lockscreen.xml /usr/share/desktop-base/kali-theme/lockscreen/gnome-background.xml 210
 
     # Set up an alternative for the wallpaper for Plasma 5/KDE
     update-alternatives --install \
 	/usr/share/wallpapers/DebianTheme \
-	desktop-plasma5-wallpaper /usr/share/desktop-base/active-theme/wallpaper 210
+	desktop-plasma5-wallpaper /usr/share/desktop-base/kali-theme/wallpaper 210
 
     # Login theme
     # Highest priority for active theme
     update-alternatives --install /usr/share/images/desktop-base/login-background.svg \
-	desktop-login-background /usr/share/desktop-base/active-theme/login/background.svg 210
+	desktop-login-background /usr/share/desktop-base/kali-theme/login/background.svg 210
 
     # Set up an alternative for the GRUB background/colors config
     # Highest priority for active theme