[headless] Remove altimin@ from active owners.

R=alexclarke@chromium.org

Change-Id: I77cf2e26643a862217d009cc7539fd838d3c1583
Reviewed-on: https://chromium-review.googlesource.com/1042189
Commit-Queue: Alexander Timin <altimin@chromium.org>
Reviewed-by: Alex Clarke <alexclarke@chromium.org>
Cr-Commit-Position: refs/heads/master@{#555747}

headless/OWNERS

 skyostil@chromium.org
 alexclarke@chromium.org
-altimin@chromium.org
 eseckler@chromium.org
 
 # Emeritus:
+altimin@chromium.org
 dvallet@chromium.org
 irisu@chromium.org
 jzfeng@chromium.org