[FIX] Add _id to bids_participant and bids_session in example proc status file

[alyssadai]

• Related to [FIX] Add missing _id suffix to processing status file column mappings bagel-cli#370
• See also [ENH] Add _id suffix to bids_participant and bids_session nipoppy/nipoppy#382

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• PR has an interpretable title with a prefix ([ENH], [FIX], [REF], [TST], [CI], [MNT], [INF], [MODEL], [DOC]) (see our Contributing Guidelines for more info)
• PR links to GitHub issue with mention Closes #XXXX
• Tests pass
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• Tests have been added

For bug fixes:

• There is at least one test that would fail under the original bug conditions.

[surchs]

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