Enable Sphinx man_show_urls config

URLs are not rendered in our man pages.  Let's tell Sphinx to include links
in the output until https://github.com/sphinx-doc/sphinx/pull/12108 is widely
available.

doc_src/conf.py

@@ -178,6 +178,8 @@ def get_command_description(path, name):
 # Unbreak it (#7996)
 man_make_section_directory = False
 
+man_show_urls = True
+
 # One entry per manual page. List of tuples
 # (source start file, name, description, authors, manual section).
 man_pages = [