AM/PM is case sensitive

[Kannan171]

Typing "pm" instead of "PM" is expected to be accepted but the command does not accept this.

To reproduce:

badd d/2021-10-01 3:00 pm p/87438807 x/5

Expected: Accept the time as 3pm
Actual : Rejected as it is not 3:00 PM

[nus-se-bot]

Your response not required for this bug as the team has accepted the bug as it is.