Update docs config.

Newer `Sphinx` versions marked some of our settings as depricated and
offer new stuff.

docs/conf.py

@@ -53,7 +53,7 @@ master_doc = 'index'
 
 # General information about the project.
 project = 'diceware'
-copyright = '2015-2023, Uli Fouquet'
+copyright = '2015-2024, Uli Fouquet'
 
 # The version info for the project you're documenting, acts as replacement for
 # |version| and |release|, also used in various other places throughout the
@@ -69,7 +69,7 @@ release = version
 #
 # This is also used if you do content translation via gettext catalogs.
 # Usually you set "language" from the command line for these cases.
-language = None
+language = 'en'
 
 # There are two options for replacing |today|: either, you set today to some
 # non-false value, then it is used:
@@ -357,4 +357,4 @@ epub_exclude_files = ['search.html']
 
 
 # Example configuration for intersphinx: refer to the Python standard library.
-intersphinx_mapping = {'http://docs.python.org/': None}
+intersphinx_mapping = {'python': ('https://docs.python.org/3', None)}