Limit spikesorting artifacts to valid timestamps

[samuelbray32]

Description

Fixes #1176

• In artifact detection, clip intervals going past the valid timestamps to the last valid timepoint
• prevents error when artifact interval window buffer goes past the end of the timestamps

Checklist:

• N This PR should be accompanied by a release: (yes/no/unsure)
• NA If release, I have updated the CITATION.cff
• N This PR makes edits to table definitions: (yes/no)
• NA If table edits, I have included an alter snippet for release notes.
• NA If this PR makes changes to position, I ran the relevant tests locally.
• I have updated the CHANGELOG.md with PR number and description.
• NA I have added/edited docs/notebooks to reflect the changes