Bump electron from 9.1.1 to 15.5.5 in /GUI

Bumps [electron](https://github.com/electron/electron) from 9.1.1 to 15.5.5.
- [Release notes](https://github.com/electron/electron/releases)
- [Changelog](https://github.com/electron/electron/blob/main/docs/breaking-changes.md)
- [Commits](https://github.com/electron/electron/compare/v9.1.1...v15.5.5)

---
updated-dependencies:
- dependency-name: electron
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

GUI/package.json

@@ -20,7 +20,7 @@
     "chart.js": "^2.9.3",
     "chartjs-plugin-streaming": "^1.8.0",
     "core-js": "^3.6.5",
-    "electron": "^9.1.1",
+    "electron": "^15.5.5",
     "file-saver": "^2.0.2",
     "socket.io-client": "^3.0.4",
     "typeface-roboto": "0.0.75",
@@ -39,7 +39,7 @@
     "@vue/cli-plugin-router": "^4.4.6",
     "@vue/cli-service": "~4.4.0",
     "babel-eslint": "^10.1.0",
-    "electron": "^9.0.0",
+    "electron": "^15.5.5",
     "electron-devtools-installer": "^3.1.0",
     "electron-icon-builder": "^1.0.2",
     "eslint": "^6.7.2",