docs: add sha256 checksums for 17.1.8

Signed-off-by: Andres Gomez <agomez@igalia.com>
(cherry picked from commit 44e008e85efe141087d8ebe52e273e0020029481)
diff --git a/docs/relnotes/17.1.8.html b/docs/relnotes/17.1.8.html
index 1e3ec6d..b8dfe0c 100644
--- a/docs/relnotes/17.1.8.html
+++ b/docs/relnotes/17.1.8.html
@@ -31,7 +31,8 @@
 
 <h2>SHA256 checksums</h2>
 <pre>
-TBD
+faa59a677e88fd5224cdfebcdb6ca9ad3e3c64bd562baa8d5c3c1faeef1066b6  mesa-17.1.8.tar.gz
+75ed2eaeae26ddd536150f294386468ae2e1a7717948c41cd14b7875be5269db  mesa-17.1.8.tar.xz
 </pre>