Replace outdated stumpy.mplstyle URL in notebooks

[strangertomycode]

Fixes #1139

Summary

Replaced outdated stumpy.mplstyle URL references in the listed notebooks:

From:

https://raw.githubusercontent.com/TDAmeritrade/stumpy/main/docs/stumpy.mplstyle

To:

https://raw.githubusercontent.com/stumpy-dev/stumpy/main/docs/stumpy.mplstyle

Verification

• Forked, cloned, and checked out the latest code
• Created a new branch
• Made the requested notebook updates
• Installed black
• Installed flake8
• Installed pytest-cov
• Ran black --exclude=".*\.ipynb" --extend-exclude=".venv" --diff ./
• Ran flake8 --extend-exclude=.venv ./

Notes

./setup.sh dev && ./test.sh was attempted. Black, isort, and flake8 checks completed successfully. The test suite could not be completed locally due to missing optional test dependencies (tornado, followed by dask.distributed) during test collection. No source code functionality was modified; this PR only updates notebook URL references.

[gitnotebooks]

Found 17 changed notebooks. Review the changes at https://app.gitnotebooks.com/stumpy-dev/stumpy/pull/1141

[seanlaw]

@strangertomycode Thank you for your PR. It appears that there are big changes in several of the notebooks that make it impossible to review. However, the issue should simply require opening the .ipynb file as a plain text file (rather than inside of Jupyter) and replacing the text. Otherwise, if you execute it as a notebook then large images also get marked as a change and I cannot review it since it will not show up for me in Github.