Update models used for embeddings in the weaviate example (langchain-ai#3594)

Use text-embedding-ada-002 because it [outperforms all other
models](https://openai.com/blog/new-and-improved-embedding-model).

Author: hsm207

docs/modules/indexes/vectorstores/examples/weaviate.ipynb

@@ -75,7 +75,8 @@
     "            \"vectorizer\": \"text2vec-openai\",\n",
     "              \"moduleConfig\": {\n",
     "                \"text2vec-openai\": {\n",
-    "                  \"model\": \"babbage\",\n",
+    "                  \"model\": \"ada\",\n",
+    "                  \"modelVersion\": \"002\",\n",
     "                  \"type\": \"text\"\n",
     "                }\n",
     "              },\n",