Currently, if you email a report with a saved filter, the email will show all of the filters selected in center aligned black text at the top of the email. It's not customizable. It's not possible to hide it. The list of filters may be long and interrupt the flow of information in the email. We can instead use filters in the cards themselves, but it's tedious to maintain the filters of many cards on a dashboard when we could just use 1 saved filter for the whole dashboard.
If the content can't be hidden then putting it at the bottom, then changing the text to white, left-aligning it, or making the font smaller would still look better.