Disregards template validity in the context of the FSE editor

This is VERY much a hack around
WordPress/gutenberg#11681

Previously, it was fine to do this just once at the beginning. But we
discovered that it also happens when performing undo.
Granted, performing undo might do something else, but my best guess is
that it's related to the above issue.

apps/full-site-editing/full-site-editing-plugin/full-site-editing/editor/template-validity-override/index.js

@@ -19,7 +19,5 @@ const unsubscribe = subscribe( () => {
 	}
 	if ( select( 'core/editor' ).isValidTemplate() === false ) {
 		dispatch( 'core/editor' ).setTemplateValidity( true );
-		// should only need to do this once
-		unsubscribe();
 	}
 } );