fix(design-tenets): remove note of video below (#12028)

As there is no video below, remove the notice

Author: constantinius

develop-docs/frontend/design-tenets.mdx

@@ -58,7 +58,7 @@ Why minimize content refreshes?
 Spinners should be used carefully. Having multiple spinners on the page is distracting. Reserve spinners for primary content that has an unknown height. Favor the usage of sized placeholder elements where the height of content is known, or the content is secondary to the main goal of the page.
 
 Why use placeholders?
-- Less layout shifts / render thrash (see video below)
+- Less layout shifts / render thrash
 - Better perceived performance
 - Avoids having multiple loading spinner animations at once, which looks ugly