Birmingham | 26-ITP-May |Gabriel Pawuoi | Sprint 1 | implement dedupe function and tests

[KhotKeys]

Learners, PR Template

Self checklist

• I have titled my PR with Region | Cohort | FirstName LastName | Sprint | Assignment Title
• My changes meet the requirements of the task
• I have tested my changes
• My changes follow the style guide

Changelist

• Implemented the dedupe function using a Set to remove duplicate values while preserving the order of first occurrences.

• Added tests covering an empty array, an array with no duplicates, and arrays of strings and numbers with duplicates.

[LonMcGregor]

See my comment on #1398

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[github-actions]

Your PR couldn't be matched to an assignment in this module.

Please check its title is in the correct format, and that you only have one PR per assignment.

If this PR is not coursework, please add the NotCoursework label (and message on Slack in #cyf-curriculum or it will probably not be noticed).

If this PR needs reviewed, please add the 'Needs Review' label to this PR after you have resolved the issues listed above.