Update MailItemsAccessedTimeSeries.yaml

[shainw]

Required items, please complete

Change(s):

• Updated URL in description

Reason for Change(s):

• Incorrect URL

Version Updated:

• Yes

Testing Completed:

• No query change

Checked that the validations are passing and have addressed any issues that are present:

• Yes

[contentautomationbot]

Hello how are you I am GitHub bot
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I see that you changed templates under the detections/analytic rules folder. Did you remember to update the version of the templates you changed?
If not, and if you want customers to be aware that a new version of this template is available, please update the version property of the template you changed.