Update year in copyright (glad that 2020 is over)

Cito · Cito · commit 48dea0eb6ab7 · 2021-02-06T18:17:08.000+01:00
diff --git a/docs/conf.py b/docs/conf.py
@@ -51,7 +51,7 @@
 
 # General information about the project.
 project = 'GraphQL-core 3'
-copyright = '2020, Christoph Zwerschke'
+copyright = '2021, Christoph Zwerschke'
 author = 'Christoph Zwerschke'
 
 # The version info for the project you're documenting, acts as replacement for
