upgrade react-split (#12054)

superset-frontend/package-lock.json

@@ -30618,7 +30618,7 @@
       "dependencies": {
         "core-js": {
           "version": "1.2.7",
-          "resolved": "https://registry.npmjs.org/core-js/-/core-js-1.2.7.tgz",
+          "resolved": "http://registry.npmjs.org/core-js/-/core-js-1.2.7.tgz",
           "integrity": "sha1-ZSKUwUZR2yj6k70tX/KYOk8IxjY="
         }
       }

superset-frontend/package.json

@@ -152,7 +152,7 @@
     "react-select": "^3.1.0",
     "react-select-async-paginate": "^0.4.1",
     "react-sortable-hoc": "^1.11.0",
-    "react-split": "^2.0.4",
+    "react-split": "^2.0.9",
     "react-sticky": "^6.0.3",
     "react-syntax-highlighter": "^15.3.0",
     "react-table": "^7.2.1",