Update Gutenberg SHA in package.json

Author: ellatrix

package.json

@@ -7,7 +7,7 @@
 		"url": "https://develop.svn.wordpress.org/trunk"
 	},
 	"gutenberg": {
-		"sha": "7e09b9b26948845d3de48d089cb4472af93a62b7",
+		"sha": "c15cef1d6b07f666df28dac0383bafb0edfe0914",
 		"ghcrRepo": "WordPress/gutenberg/gutenberg-wp-develop-build"
 	},
 	"engines": {