The second letter at start of each line of output is the status. ‘i’ means installed. ‘c’ means configuration files remain (but kernel has been removed).
So, most of the items you list here are kernels already removed, but the configuration files are still there.
(Your command would not list any old ‘linux-signed-image’ files and and ‘linux-header’ files which might also be installed, so don’t forget those.)
To remove with Synaptic Package Manager always select ‘mark for complete removal’ as the removal option. This removes the configuration files also.
To remove old configuration files that remain behind, you can use a terminal command like this:
sudo apt-get purge linux-image-4.4.0-104-generic
and the config. files for this kernel will be removed even if the kernel itself is already gone.