Fix DeprecationWarning in local_weighted_learning.py

[tianyizheng02]

Describe your change:

Recent build logs (e.g., this one) show that machine_learning/local_weighted_learning/local_weighted_learning.py produces a DeprecationWarning:

machine_learning/local_weighted_learning/local_weighted_learning.py::machine_learning.local_weighted_learning.local_weighted_learning.local_weight_regression
machine_learning/local_weighted_learning/local_weighted_learning.py::machine_learning.local_weighted_learning.local_weighted_learning.local_weight_regression
machine_learning/local_weighted_learning/local_weighted_learning.py::machine_learning.local_weighted_learning.local_weighted_learning.local_weight_regression
  /home/runner/work/Python/Python/machine_learning/local_weighted_learning/local_weighted_learning.py:125: DeprecationWarning: Conversion of an array with ndim > 0 to a scalar is deprecated, and will error in future. Ensure you extract a single element from your array before performing this operation. (Deprecated NumPy 1.25.)
    y_pred[i] = item @ local_weight(item, x_train, y_train, tau)

This warning occurs because the output of @, which is an np.ndarray, is being implicitly converted to a scalar. This PR replaces @ with np.dot() to resolve this warning.

• Add an algorithm?
• Fix a bug or typo in an existing algorithm?
• Documentation change?

Checklist:

• I have read CONTRIBUTING.md.
• This pull request is all my own work -- I have not plagiarized.
• I know that pull requests will not be merged if they fail the automated tests.
• This PR only changes one algorithm file. To ease review, please open separate PRs for separate algorithms.
• All new Python files are placed inside an existing directory.
• All filenames are in all lowercase characters with no spaces or dashes.
• All functions and variable names follow Python naming conventions.
• All function parameters and return values are annotated with Python type hints.
• All functions have doctests that pass the automated testing.
• All new algorithms include at least one URL that points to Wikipedia or another similar explanation.
• If this pull request resolves one or more open issues then the description above includes the issue number(s) with a closing keyword: "Fixes #ISSUE-NUMBER".

[tianyizheng02]

@ChrisO345 I just took a look at this PR's build logs and apparently the DeprecationWarning is still there, even with the new np.dot function call. I'll open a new PR to try to fix it again, and I'll request your review once I confirm that it's actually fixed.