Prompt should indicate default option

[Whissi]

Note this is tested with v0.4.3 but I didn't spot any significant changes in current master so I assume this is still happening in current master:

1. Run eclean-kernel --ask --destructive --all.
2. You will get prompted like

   Remove 5.11.15-gentoo-x86_64 (unwanted)? [Yes/No]

3. When you now press Enter, output will be

   • Removing kernel 5.11.15-gentoo-x86_64 (unwanted)

   • /boot/vmlinuz-5.11.15-gentoo-x86_64
   • /boot/System.map-5.11.15-gentoo-x86_64
   • /boot/initramfs-5.11.15-gentoo-x86_64.img
   • /lib/modules/5.11.15-gentoo-x86_64
   • /usr/src/linux-5.11.15-gentoo

This could be unexpected. How about indicating default action like known from make oldconfig? I.e. instead of

[Yes/No]

show

[YES/no]

so it should be clear that pressing Enter without any further input will proceed with removal.