Remove stale comment

Author: m-akinc

packages/nimble-components/src/utilities/tests/intersection-observer.ts

@@ -17,10 +17,6 @@ export async function checkFullyInViewport(
                     resolve(false);
                 }
             },
-            // As of now, passing a document as root is not supported on Safari:
-            // https://developer.mozilla.org/en-US/docs/Web/API/Intersection_Observer_API#browser_compatibility
-            // If we begin running these tests on Safari, we may need to skip those that use this function.
-            // This issue tracks expanding testing to Safari: https://github.com/ni/nimble/issues/990
             { threshold: 1.0, root: document }
         );
         intersectionObserver.observe(element);