Replace myself with sdefresne in rlz/OWNERS

I haven't worked on this code in years and am doing a very poor job
at doing reviews here.

Bug: none
Change-Id: I6dfdbe5b173ee5826205b337a6d1222bea2bf48f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2468057Reviewed-by: Sylvain Defresne <sdefresne@chromium.org>
Reviewed-by: Roger Tawa <rogerta@chromium.org>
Commit-Queue: Nico Weber <thakis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#816570}

rlz/OWNERS

 rogerta@chromium.org
-thakis@chromium.org
+sdefresne@chromium.org
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