perf(validation): stop reloading PDP course CSV for each datetime format

[mrmaloof]

Description

• Drop the API-side PDP course datetime-format loop in _read_pdp_course_edvise; formats are handled by edvise read_raw_pdp_course_data.
• Call handling_duplicates(df) with the current one-arg signature.

Asana Task

Investigate file upload timeout issue TSU + GVSU - EDVISEBUILD-6069

Deployment Readiness*

Testing

Describe or check:

• Created or updated unit, feature, and/or integration tests
• Typical manual testing in the local env browser, dev pipeline, etc.

Deployment Notes

Describe or check:

Depends on edvise#266 (or a release that includes it).

Rollback Plan

Describe or check:

• Standard revert is sufficient (git revert)

Reviewer Guidance / Questions*

Screenshots / Testing Evidence*

SOC 2 Change Management Checklist

• None of the below are true in this code
• New roles/permissions are introduced without review and approval by the product manager
• Hardcoded credentials, secrets, or API keys are present in this code
• Secrets are being managed outside of the approved secrets management process (e.g., GitHub Secrets, environment variables)
• PII or sensitive data handling is introduced or changed without being reviewed against our data classification policy
• Sensitive data is written to logs
• Input validation and sanitization is missing
• An unnecessary attack surface has been introduced (e.g., unused endpoints, open ports, debug modes left enabled)
• Common vulnerabilities have been introduced in the code (inc. any dependencies added or updated)
• No review for common vulnerabilities has been conducted
• Not tested in a non-production environment
• Breaking changes to existing APIs or integrations with downstream consumers being notified
• Performance impact has not been considered or acceptable
• Appropriate audit logging is missing for any security-relevant actions introduced by this change
• Log entries contain sensitive or PII data
• All existing tests do not pass locally (./vendor/bin/pest)

Provide justification if you are submitting a PR with any boxes checked other than the first.

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*Optional

[vishpillai123]

why is the implementation only for course and not cohort as well?