Replace HTTP links with HTTPS ones: Documentation/sphinx/parse-headers.pl

Rationale:
Reduces attack surface on kernel devs opening the links for MITM
as HTTPS traffic is much harder to manipulate.

Deterministic algorithm:
For each file:
  For each line:
    If doesn't contain `\bxmlns\b`:
      For each link, `\bhttp://[^# \t\r\n]*(?:\w|/)`:
        If both the HTTP and HTTPS versions
        return 200 OK and serve the same content:
          Replace HTTP with HTTPS.
Signed-off-by: Alexander A. Klimov <grandmaster@al2klimov.de>
Link: https://lore.kernel.org/r/20200620075402.22347-1-grandmaster@al2klimov.deSigned-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/sphinx/parse-headers.pl

@@ -393,7 +393,7 @@ Report bugs to Mauro Carvalho Chehab <mchehab@kernel.org>
 
 Copyright (c) 2016 by Mauro Carvalho Chehab <mchehab+samsung@kernel.org>.
 
-License GPLv2: GNU GPL version 2 <http://gnu.org/licenses/gpl.html>.
+License GPLv2: GNU GPL version 2 <https://gnu.org/licenses/gpl.html>.
 
 This is free software: you are free to change and redistribute it.
 There is NO WARRANTY, to the extent permitted by law.