server: Remove dependency to "open", closes #221

This is a very old dependency from 2018:
TriliumNext/Trilium@aa2bbc6

It is no longer used.

Author: eliandoran

package-lock.json

@@ -82,7 +82,6 @@
     "multer": "1.4.5-lts.1",
     "node-abi": "3.56.0",
     "normalize-strings": "1.1.1",
-    "open": "8.4.1",
     "panzoom": "9.4.3",
     "print-this": "2.0.0",
     "rand-token": "1.0.1",