Added .default scope to URI to get token using DefaultAzureCredential

Fixing issue encountered when using this in some contexts (like virtual environments in notebooks).

Author: achandmsft

examples/azure/finetuning.ipynb

@@ -58,7 +58,7 @@
     "from azure.identity import DefaultAzureCredential\n",
     "\n",
     "default_credential = DefaultAzureCredential()\n",
-    "token = default_credential.get_token(\"https://cognitiveservices.azure.com\")\n",
+    "token = default_credential.get_token(\"https://cognitiveservices.azure.com/.default\")\n",
     "\n",
     "openai.api_type = 'azure_ad'\n",
     "openai.api_key = token.token\n",