[wasm-gc] Change ref.cast_nop from 0xfb48 to 0xfb4c

ref.cast_nop is used for internal testing only.
0xfb48 will become ref.test null.

Bug: v8:7748
Change-Id: Iaee762dd97a993a361edddf656090210876178a2
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3913205Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Auto-Submit: Matthias Liedtke <mliedtke@chromium.org>
Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/main@{#83430}

src/wasm/wasm-opcodes.h

@@ -711,7 +711,7 @@ bool V8_EXPORT_PRIVATE IsJSCompatibleSignature(const FunctionSig* sig,
   V(RefCast, 0xfb45, _, "ref.cast")                                            \
   V(BrOnCast, 0xfb46, _, "br_on_cast")                                         \
   V(BrOnCastFail, 0xfb47, _, "br_on_cast_fail")                                \
-  V(RefCastNop, 0xfb48, _, "ref.cast_nop")                                     \
+  V(RefCastNop, 0xfb4c, _, "ref.cast_nop")                                     \
   V(RefIsData, 0xfb51, _, "ref.is_data")                                       \
   V(RefIsI31, 0xfb52, _, "ref.is_i31")                                         \
   V(RefIsArray, 0xfb53, _, "ref.is_array")                                     \

test/mjsunit/wasm/wasm-module-builder.js

@@ -511,7 +511,7 @@ let kExprRefTest = 0x44;
 let kExprRefCast = 0x45;
 let kExprBrOnCast = 0x46;
 let kExprBrOnCastFail = 0x47;
-let kExprRefCastNop = 0x48;
+let kExprRefCastNop = 0x4c;
 let kExprRefIsData = 0x51;
 let kExprRefIsI31 = 0x52;
 let kExprRefIsArray = 0x53;