[8.x] [embeddable] remove legacy embeddable compatibility layer (#204642

) (#204815)

# Backport

This will backport the following commits from `main` to `8.x`:
- [[embeddable] remove legacy embeddable compatibility layer
(#204642)](#204642)

<!--- Backport version: 9.4.3 -->

### Questions ?
Please refer to the [Backport tool
documentation](https://github.com/sqren/backport)

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remove legacy embeddable compatibility layer
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remove legacy embeddable compatibility
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remove legacy embeddable compatibility layer
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remove legacy embeddable compatibility layer
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Co-authored-by: Nathan Reese <[email protected]>

src/plugins/embeddable/public/index.ts

@@ -93,9 +93,4 @@ export function plugin(initializerContext: PluginInitializerContext) {
   return new EmbeddablePublicPlugin(initializerContext);
 }
 
-export {
-  embeddableInputToSubject,
-  embeddableOutputToSubject,
-} from './lib/embeddables/compatibility/embeddable_compatibility_utils';
-
 export { COMMON_EMBEDDABLE_GROUPING } from './lib/embeddables/common/constants';