(core) fix some tests for node v14

Test Plan: existing tests pass

Reviewers: dsagal

Reviewed By: dsagal

Differential Revision: https://phab.getgrist.com/D2814

app/server/lib/NSandbox.ts

@@ -173,6 +173,7 @@ export class NSandbox implements ISandbox {
       if (this._isWriteClosed) { resolve(); }
       this.childProc.on('error', reject);
       this.childProc.on('close', resolve);
+      this.childProc.on('exit', resolve);
       this._close();
     });
 

package.json

@@ -99,7 +99,7 @@
     "moment-timezone": "0.5.21",
     "morgan": "1.9.1",
     "mousetrap": "1.6.2",
-    "multiparty": "4.2.1",
+    "multiparty": "4.2.2",
     "node-fetch": "2.2.0",
     "numeral": "2.0.6",
     "plotly.js-basic-dist": "1.51.1",