You don't have two DKMS modules. You have one DKMS module built for two different kernel versions.
As a rule of thumb you shouldn't manually uninstall DKMS modules for kernels that are still installed unless you have a specific reason.
If you really want to uninstall the module for a particular kernel, you can refer to the
The kernel and arch to perform the action upon. You can specify multiple kernel version/arch pairs on the command line by repeating the
-k argument with a different kernel version and arch. However, not all actions support multiple kernel versions (it will error out in this case). The arch part can be omitted, and DKMS will assume you want it to be the arch of the currently running system.
So the command to uninstall the module in question for kernel
dkms uninstall -k 4.4.0-45-generic rtl8812AU
You can omit the module version since you can't install multiple versions of a module for the same kernel anyway.