Disable journaling on ext4 filesystem partition
As written in the manpages mke2fs is used for creating new filesystems, not changing existing ones.
I think the tool you are looking for is tune2fs, it can use the same parameter:
tune2fs -O ^has_journal /dev/sdXY
Whatever you do, make a backup before you play with filesystems.
You might have to use the -f (force) parameter.
Check the manpages with man tune2fs before using the tool (and make a backup, seriously).