You can opt out of direct deal invites entirely on your Investor Settings page. Click on your avatar on the far right side of the header, click "Investor Settings," and unselect "All Syndicates" in the Deal Source section at the top.
Instead of opting out entirely, you can also control which direct deal invites you receive by updating your investment thesis. Click on your avatar on the far right side of the header, click "Investor Settings," and adjust your filters as you wish.