Rename @initial to @starting-style

site/en/blog/whats-new-css-ui-2023/index.md

@@ -595,13 +595,13 @@ In order for all of this to transition popovers in and out smoothly, the web nee
 
 As a part of the work to enable nice transitions for popovers, selectmenus, and even existing elements like dialogs or custom components, browsers are enabling new plumbing to support these animations.
 
-The following popover demo, animates popovers in and out using `:popover-open` for the open state, `@initial` for the before-open state, and applies a transform value to the element directly for the after-open-is-closed state. To make this all work with display, it needs adding to the `transition` property, like so:
+The following popover demo, animates popovers in and out using `:popover-open` for the open state, `@starting-style` for the before-open state, and applies a transform value to the element directly for the after-open-is-closed state. To make this all work with display, it needs adding to the `transition` property, like so:
 
 ```css
 .settings-popover {
   &:popover-open {
     /*   0. before-change   */
-    @initial {
+    @starting-style {
       transform: translateY(20px);
       opacity: 0;
     }
@@ -631,10 +631,6 @@ The following popover demo, animates popovers in and out using `:popover-open` f
   tab: 'result'
 } %}
 
-{% Aside 'caution' %}
-This is currently an experimental API, and the syntax for `@initial` might change before going stable.
-{% endAside %}
-
 ## Interactions
 
 Which brings us to interactions, the last stop on this tour of web UI features.