doc hash-function-transition: note the lack of a changelog

The changelog embedded in the document pre-dates the addition of the
document to git.git (it used to be a Google Doc), so it only goes up
to 752414ae43 ("technical doc: add a design doc for hash function
transition", 2017-09-27).

Since then I made some small edits to it, which would have been worthy
of including in this changelog (but weren't). Instead of amending it
to include these, just note that future changes will be noted in the
log.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/technical/hash-function-transition.txt

@@ -814,6 +814,12 @@ Incorporated suggestions from jonathantanmy and sbeller:
 * avoid loose object overhead by packing more aggressively in
   "git gc --auto"
 
+Later history:
+
+ See the history of this file in git.git for the history of subsequent
+ edits. This document history is no longer being maintained as it
+ would now be superfluous to the commit log
+
 [1] http://public-inbox.org/git/CA+55aFzJtejiCjV0e43+9oR3QuJK2PiFiLQemytoLpyJWe6P9w@mail.gmail.com/
 [2] http://public-inbox.org/git/CA+55aFz+gkAsDZ24zmePQuEs1XPS9BP_s8O7Q4wQ7LV7X5-oDA@mail.gmail.com/
 [3] http://public-inbox.org/git/20170306084353.nrns455dvkdsfgo5@sigill.intra.peff.net/