Revert "Fix outdated leveldown dependency"

This reverts commit a6d98db6a9.

package.json

@@ -36,7 +36,7 @@
     "html5-validator": "^1.0.7",
     "ini": "^1.3.5",
     "jsonwebtoken": "^8.2.1",
-    "leveldown": "^3.0.1",
+    "leveldown": "^1.9.0",
     "linvodb3": "^3.25.1",
     "luamin": "^1.0.4",
     "mkdirp": "^0.5.1",