Notebook usability improvements

[hemidactylus]

• credentials are not aligned to the "api_endpoint + token" (currently stuff such as region is exposed, the api url is constructed, etc). Probably can adapt this part from https://github.com/hemidactylus/mini-demo-astradb-langchain/blob/main/AstraDB_langchain_quickstart_1.ipynb

• Related: there should be no mention of keyspaces or namespaces anywhere (text nor code), it's a concept 100% hidden from user

• intro paragraph links to cassio, it shouldn't at all (for prerequisites link to e.g. https://docs.datastax.com/en/astra/home/astra.html if nothing more to the point)

• Indentation: there are several lines arranged such as

json_query = {
        "_id": "4",
        "name": "Coded Cleats Copy",
        "description": "ChatGPT integrated sneakers that talk to you",
        "$vector": [0.25, 0.25, 0.25, 0.25, 0.25],
    }

which I think style would have as

json_query = {
    "_id": "4",
    "name": "Coded Cleats Copy",
    "description": "ChatGPT integrated sneakers that talk to you",
    "$vector": [0.25, 0.25, 0.25, 0.25, 0.25],
}

• Add --quiet to the pip install to avoid a wall of useless output junk