docs: Add sha256sums for the 10.6.0 release

Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
(cherry picked from commit 5d327b373531861f86a726db669b3d656f1b5f8d)

docs/relnotes/10.6.0.html

@@ -31,9 +31,10 @@ because compatibility contexts are not supported.
 </p>
 
 
-<h2>MD5 checksums</h2>
+<h2>SHA256 checksums</h2>
 <pre>
-TBD.
+9bc659abdba26202509304f259723aaa4343dba6aac4bd87d5baea11d23c8c63  mesa-10.6.0.tar.gz
+f37e2633978deed02ff0522abc36c709586e2b555fd439a82ab71dce2c866c76  mesa-10.6.0.tar.xz
 </pre>