Update link to new issue

Co-authored-by: Richard van der Hoff <1389908+richvdh@users.noreply.github.com>

cypress/e2e/read-receipts/new-messages.spec.ts

@@ -374,7 +374,7 @@ describe("Read receipts", () => {
                 // Then the room becomes unread
                 assertUnread(room2, 1);
             });
-            // Flaky: disabled - https://github.com/vector-im/element-web/issues/26691
+            // Flaky: disabled - https://github.com/vector-im/element-web/issues/26679
             it.skip("Sending a new different-thread message after marking as read makes it unread", () => {
                 // Given 2 threads exist, and Thread2 has the latest message in it
                 goTo(room1);