Inconsistent Error Messages for `task delete`

[nus-pe-bot]

Steps to Reproduce

Assuming you only have 5 tasks in your application, run:

1. delete task 0
2. delete task 10

Expected

Both commands are invalid in the exact same way - since the task index is invalid in both cases - and so we expect both commands to show the exact same error message. However, the error message for both are different, which might confuse users as to why the 2 numbers are being treated differently even though they're both invalid. Low priority since it does not hinder the usage.

Actual

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_{[original: nus-cs2103-AY2223S1/pe-interim#5613] [original labels: type.FeatureFlaw severity.Low]}

[limweijun]

Team's Response

It's clear in the user guide that the command expects a positive integer, and hence the error is shown asking you to input a positive integer before checking for valid index

Duplicate status (if any):

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