Can remark modules already taken, which is supposed to be a feature only on planned module

[sistine-yu]

Steps to reproduce: taken cs2113 y/2 s/1 g/a mark cs2113 g/b

Expected: The program should tell me that the course is already taken and the grade cannot be updated, as the user guide says "module must have been added to the planner using the plan command."

Actual: Can successfully edit the grade.

[nus-se-bot]

Team's Response

Intended behaviour. Allows users to edit the grade in case of adding the wrong grade initially.

Items for the Tester to Verify

:question: Issue response

Team chose [response.Rejected]

• [ ] I disagree

Reason for disagreement: [replace this with your explanation]

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