Remove some residuals from update scripts

I think we have some residual, and we remove this chunk in update scripts (tools/update-packaging/common.sh):

  is_extension=$(echo "$f" | grep -c 'distribution/extensions/.*/')
  if [ $is_extension = "1" ]; then
    # Use the subdirectory of the extensions folder as the file to test
    # before performing this add instruction.
    testdir=$(echo "$f" | sed 's/\(.*distribution\/extensions\/[^\/]*\)\/.*/\1/')
    verbose_notice "     add-if \"$testdir\" \"$f\""
    echo "add-if \"$testdir\" \"$f\"" >> "$filev3"
  else
    verbose_notice "        add \"$f\"$forced"
    echo "add \"$f\"" >> "$filev3"
  fi

If I understand correctly this checks for extension directories, but we don't have them any (anymore? Was HTTPS Everywhere a directory there at a certain point? IIRC it was a directory inside omni.ja).

So, I think this could be removed.