Remove `notebooks-enabled=1` from `jupyter.conf`

In the 2024.09.0 Workbench release notes, Jupyter Hub support is being removed, by default:

Added support for Jupyter Notebook 7. (rstudio-pro#6266)
Replaced code server binary with PWB Code Server. PWB Code Server is bundled with the PWB VS Code Extension, so a separate install is no longer required. It is a fork of VS Code 1.93.0. (rstudio-pro#6265)
In VS Code sessions, Workbench now preserves the open directory or workspace on a per-session basis. (rstudio-pro#6491)
Fixed an issue preventing potential data leakage between users in the same browser session. (vscode-server#17)
Disabled Jupyter Notebooks by default on fresh installs of PWB. (rstudio-pro#6269)

Correspondingly, the product default for notebooks-enabled is 0 - docs

Accordingly, I'd propose updating the values in the helm charts to align: https://github.com/search?q=repo%3Arstudio%2Fhelm%20notebooks-enabled&type=code

Impact: We had removed our setting for notebooks-enabled to leverage the default of 0; but, it was still unexpectedly being set to 1, since we're leveraging Posit's Helm charts as a starting point.

Search the Helm repository for notebooks-enabled and inspect the chart values and templates that set it to 1. Align those chart defaults with the documented product default of 0, then verify that rendered chart configuration no longer enables Jupyter Notebooks by default.