Fix typo in "Attachments" field

Problem/Motivation

There is an extra "e" in the Attachments field (making it Attachements). This is in both the label & name of the field on the Epic and Task entities.

Proposed resolution

We should definitely fix the labels as soon is reasonable. I suspect we should also fix the name while we're pre-release rather than leave it as a gotcha for devs or when it's more difficult to resolve everywhere.

Remaining tasks

• Update labels
• Update name and all usage/references to the field