Welcome to the forum! 
First of all, downgrading packages are unsupported. To answer your specific question about the NVIDIA package, you don’t. 550.67-4 > 550.67-5 is not an NVIDIA driver version update, it’s a kernel module update to match your currently installed kernel.
Have you tried turning it off and on again? No, seriously. You should always reboot when there are important updates like kernels, Mesa, etc.
Please see: