docs: filesystems: Replace HTTP links with HTTPS ones

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:
  If not .svg:
    For each line:
      If doesn't contain `\bxmlns\b`:
        For each link, `\bhttp://[^# \t\r\n]*(?:\w|/)`:
	  If neither `\bgnu\.org/license`, nor `\bmozilla\.org/MPL\b`:
            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/20200713113705.33773-1-grandmaster@al2klimov.deSigned-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/filesystems/caching/cachefiles.rst

@@ -348,7 +348,7 @@ data cached therein; nor is it permitted to create new files in the cache.
 
 There are policy source files available in:
 
-	http://people.redhat.com/~dhowells/fscache/cachefilesd-0.8.tar.bz2
+	https://people.redhat.com/~dhowells/fscache/cachefilesd-0.8.tar.bz2
 
 and later versions.  In that tarball, see the files::