[turbofan] Remove invalid DCHECK about result hints

https://chromium-review.googlesource.com/c/v8/v8/+/1937147 removed the
DCHECK in ProcessNamedPropertyAccess but forgot to remove the one in
ProcessKeyedPropertAccess too.

Tbr: mvstanton@chromium.org
Bug: v8:7790, chromium:1029198
Change-Id: Ia313c92969fe7d5e559e34995b39834267e6b3fd
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1940258Reviewed-by: Georg Neis <neis@chromium.org>
Commit-Queue: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65230}

src/compiler/serializer-for-background-compilation.cc

@@ -3017,8 +3017,6 @@ void SerializerForBackgroundCompilation::ProcessKeyedPropertyAccess(
 
   if (access_mode == AccessMode::kLoad) {
     environment()->accumulator_hints() = new_accumulator_hints;
-  } else {
-    DCHECK(new_accumulator_hints.IsEmpty());
   }
 }