bsp-cli: drop stale chromium master_preferences rescue block

Three lines in armbian-bsp-cli's postinst:

  if [[ -L "/usr/lib/chromium-browser/master_preferences.dpkg-dist" ]]; then
      mv /usr/lib/chromium-browser/master_preferences.dpkg-dist /usr/lib/chromium-browser/master_preferences
  fi

were shipped in 2018 (commit e7657a5) alongside
packages/bsp/common/usr/lib/chromium-browser/master_preferences.dpkg-dist,
as the tail half of a rescue pattern that dealt with chromium-browser's
conffile clashing with the armbian-supplied symlink / preseed file.
The ship-side half was removed at some point — bsp-cli no longer
packages anything under /usr/lib/chromium-browser/ — so the -L test
is never true on a fresh install. Dead code.

It's also conceptually wrong in the new world: chromium branding
(master_preferences, policies, chromium.d flags) now lives in
armbian-config (configng:tools/modules/desktops/branding/browsers/etc/).
bsp-cli shouldn't be touching chromium at all. Remove the dead
rescue.

Also drop packages/blobs/desktop/chromium/{master_preferences,initial_bookmarks.html} —
these blobs were consumed by the per-DE create_desktop_package.sh
scripts under config/desktop/, which were deleted in the first
commit of this PR. Nothing in the tree references them any more;
grep across lib/ config/ extensions/ returns zero hits.

Author: igorpecovnik

lib/functions/bsp/armbian-bsp-cli-deb.sh

@@ -460,10 +460,6 @@ function board_side_bsp_cli_postinst_finish() {
 		mv /etc/default/armbian-firstrun.dpkg-dist /etc/default/armbian-firstrun
 	fi
 
-	if [[ -L "/usr/lib/chromium-browser/master_preferences.dpkg-dist" ]]; then
-		mv /usr/lib/chromium-browser/master_preferences.dpkg-dist /usr/lib/chromium-browser/master_preferences
-	fi
-
 	# Reload services
 	systemctl --no-reload enable armbian-hardware-monitor.service armbian-hardware-optimize.service armbian-zram-config.service armbian-led-state.service > /dev/null 2>&1
 }