Remove linux-lts from apks — kernel handled by kernel_flavors

linux-lts in apks conflicted with mkimage's own kernel download via
kernel_flavors="lts". The kernel is embedded in the ISO via modloop,
not via apks. Pinning it in apks caused "unable to select package".

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

iso/builder/mkimg.bee.sh

@@ -17,7 +17,6 @@ profile_bee() {
     syslinux_serial="0 115200"
     apks="
         alpine-base
-        linux-lts=${KERNEL_PKG_VERSION}
         linux-firmware-none
         linux-firmware-rtl_nic
         linux-firmware-bnx2