if we go on the theory that there's no room left then this sudo clr-boot-manager update should leave the last 2 kernels and vacate the rest.
as for if it's too small to begin with and/or you got to get rid of stuff manually, that's harder, and I've never walked thru that minefield personally
edit: looking at pic again I see you boot with grub. my answer might not be valid then. I don't use it. Someone does though
