Keep copyright year on original date

In accordance with copyright law, I hope.

Author: KastanDay

doc/src/sphinx/conf.py

@@ -18,7 +18,7 @@
 # -- Project information -----------------------------------------------------
 
 project = 'Clowder'
-copyright = '2021, University of Illinois at Urbana-Champaign'
+copyright = '2019, University of Illinois at Urbana-Champaign'
 author = 'Luigi Marini'
 
 # The full version, including alpha/beta/rc tags