Remove SUPPORT.md

This document is now at odds with the project being moved to
"unsupported" status which means

  "The project has reached a stable, usable state but the author(s)
   have ceased all work on it. A new maintainer may be desired."

Cc: Maryna Herasimovich <[email protected]>
Link: <https://www.repostatus.org/#unsupported>
Signed-off-by: Andrew Clayton <[email protected]>

Author: ac000

README.md

@@ -10,8 +10,6 @@
 
 # NGINX Unit is actively seeking contributors and maintainers
 
-Please see: [SUPPORT.md](/SUPPORT.md)
-
 NGINX Unit is a lightweight and versatile open-source server that has
 two primary capabilities: