[v8windbg] Fix narrowing conversion warning

Bug: chromium:1255096
Change-Id: I809fb4ef5eaa06975a3e24ad0a36d803aa791c32
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3206837
Auto-Submit: Zhi An Ng <zhin@chromium.org>
Commit-Queue: Maya Lekova <mslekova@chromium.org>
Reviewed-by: Maya Lekova <mslekova@chromium.org>
Cr-Commit-Position: refs/heads/main@{#77255}

tools/v8windbg/base/utilities.cc

@@ -138,7 +138,7 @@ HRESULT GetInt32(IDebugHostConstant* object, int* value) {
   RETURN_IF_FAIL(object->GetValue(&variant));
 
   if (variant.vt != VT_I4) return E_FAIL;
-  *value = variant.ullVal;
+  *value = variant.lVal;
   return S_OK;
 }