Your Ubuntu installation is on /dev/sda8, which is only 11 GiB in size, 9 GiB of which are already in use. Although 11 GiB is (clearly) enough for an Ubuntu installation, it's a bit tight, and whether because of temporary needs of doing an upgrade or increased needs of Ubuntu 16.04 vs. 14.04, the 2 GiB of free space on that partition is not sufficient for doing an upgrade.
In theory, you might be able to clear enough space by uninstalling unused packages, removing unnecessary files from your home directory, or taking other disk-space-saving measures; however, I don't think that's really the best approach, given your situation. I see that the partition immediately before /dev/sda8, /dev/sda7, is a 143 GiB NTFS partition with 127 GiB of free space. Unless you have plans to use most of that space in the foreseeable future, I recommend you shrink that partition and move/resize your Ubuntu partition into that space. Such operations carry some risk, so backing up any important files from both partitions before you do this is a good idea. Note that you'll need to do the resizing from a "live disk," such as the Ubuntu installer in its "try before installing" mode. Several questions and answers on this site cover partition resizing in more detail, such as:
How much should you increase the size of your Ubuntu root (/) partition? That's hard to say. Given your disk sizes, I'd say to roughly double its size, unless you have a specific reason to do otherwise. (For instance, if you expect to be using lots more space in /dev/sda7, you might want to sacrifice as little of its space as possible and expand by less -- say, 5 GiB; or if you expect to be storing bigger files in the Ubuntu partition itself, you might want to expand it by more.)
An alternative to this approach is to shrink or delete your swap partition, /dev/sda9, and grow /dev/sda8 into that space. This will gain you a maximum of 3.89 GiB, though, and you'll lose your swap space, which you might or might not need. (Swap space is most important if you use suspend-to-disk operations, but it can be used to improve overall system performance even if you don't do this, since the kernel can use it to help optimize its use of RAM.)
