fixed library target for nbclassic nbextension for graph_notebook_widget

[adityaramesh12]

Issue #, if available: Issue #738

Description of changes:
This PR addresses issues with extension loading in Jupyter Notebook Classic (NBClassic) environments. The changes modify the webpack configuration to ensure proper module definition and loading.

Key Changes:

1. Modified the first nbextension output:

   • Changed libraryTarget from "amd" to "var"
   • This ensures the extension is properly exposed as a global variable, which is necessary for NBClassic's initial extension loading process

2. Adjusted the second nbextension output:

   • Removed the library name for the AMD module (set to undefined)
   • This allows for proper AMD module definition without potential namespace conflicts

These changes align our extension with the expected module loading patterns in Jupyter notebooks, addressing potential issues where the extension might fail to load or initialize properly in certain environments.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[michaelnchin]

LGTM - let's make sure to include a changelog entry.

[adityaramesh12]

Thanks @michaelnchin ! I'll add it to the changelog in a separate PR for 5.0.1 changes/