Background gradient shows a black horizontal line glitch in Firefox

Why do I get the horizontal line glitch in Firefox 88 (on Mac) when I use a background gradient?

.tristana {
  height: 100vh;
  background: linear-gradient(180deg, #5577BA 0%, #2CA6BC 100%);
}

Demo

https://codepen.io/evgenyneu/full/eYvmYVK