"hours" does not change to "hour" when the time is 1 hour

[nus-pe-script]

Describe the bug As described in the title, there can be expressions "1 hours" in the app.

To Reproduce Steps to reproduce the behavior:

1. Type "add t/xample d/that's it c/CS2040 p/high h/1"
2. See error

Expected behavior Should be "1 hour"

Screenshots

Additional context Add any other context about the problem here.

OS and Java Version

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_{[original: dummy#31]}