Trivial typo on landing page

[bruce-usab]

On the (overview) landing page, there is a minor typo, third bullet, missing the word "in":

• You can export your report as YAML (structured data) but also as HTML (web page). Note: You will not be able to edit the report in the future without the YAML file.

[mgifford]

Thanks @bruce-usab good catch. I think this PR will fix it GSA/openacr-editor#73

I can't authorize that any more. @drewnielson want to approve that?