[cleanup][wasm] Use explicit types instead of "auto"

in function-body-decoder-impl.h.

Bug: v8:10506
Change-Id: If31aa9e35cc34f6c1c191bd487b1b01727e01dc1
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2204204
Auto-Submit: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#67838}

src/wasm/graph-builder-interface.cc

@@ -232,7 +232,8 @@ class WasmGraphBuildingInterface {
 
   void BinOp(FullDecoder* decoder, WasmOpcode opcode, const Value& lhs,
              const Value& rhs, Value* result) {
-    auto node = BUILD(Binop, opcode, lhs.node, rhs.node, decoder->position());
+    TFNode* node =
+        BUILD(Binop, opcode, lhs.node, rhs.node, decoder->position());
     if (result) result->node = node;
   }