[daggy-u] [essentials] - Update Python and Dagster versions (#19869)

## Summary & Motivation

This PR updates the Python and Dagster versions in the Requirements
portion of Dagster Essentials.

## How I Tested These Changes

docs/dagster-university/pages/dagster-essentials/lesson-2/requirements-and-installation.md

@@ -8,7 +8,7 @@ lesson: '2'
 
 To install Dagster, you’ll need:
 
-- **To install Python**. Dagster supports Python 3.8 through 3.11.
+- **To install Python**. Dagster supports Python 3.8 through 3.12.
 - **A package manager like pip or poetry**. If you need to install a package manager, refer to the following installation guides:
   - [pip](https://pip.pypa.io/en/stable/installation/)
   - [Poetry](https://python-poetry.org/docs/)
@@ -31,5 +31,5 @@ pip --version
 To install Dagster into your current Python environment:
 
 ```shell
-pip install 'dagster~=1.5'
+pip install 'dagster~=1.6'
 ```