Fix for #5289

[tumbleboy]

Description

Fixes #5289

As stated in issue 5289, tempo, _ = beat.beat_track(y=y, sr=sr) was assigning a numpy.ndarray to tempo. Trying to use Pythons built-in round() method doesn't work, so as suggested in the issue, this PR changes the line to use numpy.round() instead to get the BPM from the returning value.

We could make the fix more elaborate, as beat.beat_track() returns either a float or numpy.ndarray. Librosa docs: beat.beat_track()

To Do

• [x] Documentation.
• [x] Changelog.
• [x] Tests.

[github-actions[bot]]

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