Update the shipping version of reference types

The shipping version was incorrect in the original CL.

R=ecmziegler@chromium.org

Bug: v8:7581
Change-Id: Ib382cdacb8f6aa80718e6917b535c026b83d88cd
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3172766Reviewed-by: Emanuel Ziegler <ecmziegler@chromium.org>
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/main@{#76966}

src/wasm/wasm-feature-flags.h

@@ -94,7 +94,7 @@
   /* https://github.com/WebAssembly/reference-types */                         \
   /* V8 side owner: ahaas */                                                   \
   /* Staged in v7.8. */                                                        \
-  /* Shipped in v9.5 * */                                                      \
+  /* Shipped in v9.6 * */                                                      \
   V(reftypes, "reference type opcodes", true)                                  \
                                                                                \
   /* Threads proposal. */                                                      \