Update pinecone init details in docs (#898)

PR to fix outdated environment details in the docs, see issue #897 

I added code comments as pointers to where users go to get API keys, and
where they can find the relevant environment variable.

docs/modules/utils/combine_docs_examples/vectorstores.ipynb

@@ -483,7 +483,10 @@
     "import pinecone \n",
     "\n",
     "# initialize pinecone\n",
-    "pinecone.init(api_key=\"\", environment=\"us-west1-gcp\")\n",
+    "pinecone.init(\n",
+    "    api_key=\"YOUR_API_KEY\",  # find at app.pinecone.io\n",
+    "    environment=\"YOUR_ENV\"  # next to api key in console\n",
+    ")\n",
     "\n",
     "index_name = \"langchain-demo\"\n",
     "\n",