Admin Capabilities / unfiltered_html

I was trying to embed wistia iframes and it keeps stripping the code when I update the page. I am an admin, so checked the admin role capabilities, and unfiltered_html is not checked, but it’s grayed out and I can’t check it. I’m the admin, if I can’t change it, how??

FYI – this is not critical as I found a work around, using visual composers raw html element works, but for a lot of these pages using the composer is not necessary as I’m just changing embed code, not the page design or structure.