fix: Memory leak with old versions of yjs

Versions of yjs prior to `13.4.6` did not emit a `"destroy"` event when a doc is destroyed, meaning that doc's in the websocket servers memory are not correctly cleaned up.

package.json

@@ -54,10 +54,10 @@
     "rollup-cli": "^1.0.9",
     "standard": "^12.0.1",
     "typescript": "^3.9.6",
-    "yjs": "^13.4.1"
+    "yjs": "^13.4.6"
   },
   "peerDependenies": {
-    "yjs": "^13.0.0"
+    "yjs": "^13.4.6"
   },
   "optionalDependencies": {
     "ws": "^6.2.1",