[wasm][fuzzer] Remove duplicate call to Generate function

If the return_count is zero, the Generate will be called twice. The recent update in Generate function already handle the case inside the Generate function overload.

Change-Id: I49e0ee4a0824db60f157ea288ae6d28978c42db5
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2215816Reviewed-by: Thibaud Michaud <thibaudm@chromium.org>
Commit-Queue: Thibaud Michaud <thibaudm@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68000}

test/fuzzer/wasm-compile.cc

@@ -1592,9 +1592,6 @@ class WasmCompileFuzzer : public WasmExecutionFuzzer {
 
       WasmGenerator gen(f, function_signatures, globals, mutable_globals,
                         &function_range);
-      if (sig->return_count() == 0) {
-        gen.Generate(kWasmStmt, &function_range);
-      }
       Vector<const ValueType> return_types(sig->returns().begin(),
                                            sig->return_count());
       gen.Generate(return_types, &function_range);