fix: upgrade sortablejs from 1.15.3 to 1.15.6

Snyk has created this PR to upgrade sortablejs from 1.15.3 to 1.15.6.

See this package in npm:
sortablejs

See this project in Snyk:
https://app.snyk.io/org/newkdr/project/12a8a5f5-3e19-438c-8280-eb8f4ee06d17?utm_source=github&utm_medium=referral&page=upgrade-pr

package.json

@@ -19638,7 +19638,7 @@
 		"react-dom": "16.14.0",
 		"signal-utils": "0.20.0",
 		"slug": "10.0.0",
-		"sortablejs": "1.15.3"
+		"sortablejs": "1.15.6"
 	},
 	"devDependencies": {
 		"@eamodio/eslint-lite-webpack-plugin": "0.1.0",