Update copyright to 2023

[cconlon]

No description provided.

[JacobBarthelmeh]

Some files are missing, specifically the src/we_aes_* ones but could be a few others too.

Used the following for a list of all:

$ git grep -c Copyright | grep -v "m4\/" | grep -v COPYING | grep -v INSTALL

The number of files appear to be 48?

$ git grep -c Copyright | grep -v "m4\/" | grep -v COPYING | grep -v INSTALL | wc -l
      48

[cconlon]

Thanks! I think I caught them all with this last force push.