docs: Fix origin trial number

The listed changes aren't going to land into M97, as M96 has already been cut.

Change-Id: I7b636bf7a6da3b831ad8f121acd0f8c3f87a1423
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/66381
Auto-Submit: Ben Clayton <bclayton@google.com>
Commit-Queue: James Price <jrprice@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: James Price <jrprice@google.com>
diff --git a/docs/origin-trial-changes.md b/docs/origin-trial-changes.md
index 7b21379..40bff08 100644
--- a/docs/origin-trial-changes.md
+++ b/docs/origin-trial-changes.md
@@ -1,6 +1,6 @@
 # Tint changes during Origin Trial
 
-## Changes for M96
+## Changes for M97
 
 ### Breaking Changes