Update Help: Evernote Import - 300MB minimum file size

[pbryant-phew]

Have you read the Longevity Statement?
Sure. This is a request to improve the accuracy and usefulness of your documentation, so that can only help with longevity.

Is your feature request related to a problem? Please describe.
Update documentation to reflect the fact the minimum .enex file export size available in the Evernote app (at least on macOS) is 300MB. I'm mainly thinking of the guidance at the top of this page, which recommends a maximum .enex file size of 250MB, but there may be other locations also.

Describe the solution you'd like
Update the documentation to refer to a recommended maximum .enex file size that is actually possible to produce from Evernote.

Describe alternatives you've considered
I raised a support request and they suggested raising a feature request here.

Additional context
Screenshot of the minimum file split size in Evernote for macOS: