grub: add missed parameter 'live_rw' to 34live-rescue_rw.cfg

features.in/grub/cfg.in/34live-rescue_rw.cfg

 menuentry $"Rescue LiveCD with sessions support" --id 'rescue_session' {
   savedefault
   echo $"Loading Linux vmlinuz$KFLAVOUR ..."
-  linux /boot/vmlinuz$KFLAVOUR fastboot live @initrd_bootargs@ @stagename@=live systemd.unit=live-rescue.target ramdisk_size=@live_size@ nosplash @rescue_bootargs@ lang=$lang lowmem
+  linux /boot/vmlinuz$KFLAVOUR fastboot live @initrd_bootargs@ @stagename@=live systemd.unit=live-rescue.target ramdisk_size=@live_size@ live_rw nosplash @rescue_bootargs@ lang=$lang lowmem
   echo $"Loading initial ramdisk ..."
   initrd /boot/@initrd@$KFLAVOUR.@initrd_ext@
 }