[wasm] Remove unneeded CanonicalHandleScope

Background threads are not supposed to use any handles, so this
handle scope is not needed.

R=ahaas@chromium.org

Change-Id: I2f4776b897256684205c35633fbe1e1365abab91
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1981151Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65624}

src/wasm/module-compiler.cc

@@ -1272,10 +1272,6 @@ void CompileNativeModule(Isolate* isolate, ErrorThrower* thrower,
     if (thrower->error()) return;
   }
 
-  // Turn on the {CanonicalHandleScope} so that the background threads can
-  // use the node cache.
-  CanonicalHandleScope canonical(isolate);
-
   DCHECK_GE(kMaxInt, native_module->module()->num_declared_functions);
 
   // Install a callback to notify us once background compilation finished, or