Bump chart.js from 2.9.3 to 2.9.4 in /web-ui

Bumps [chart.js](https://github.com/chartjs/Chart.js) from 2.9.3 to 2.9.4.
- [Release notes](https://github.com/chartjs/Chart.js/releases)
- [Commits](chartjs/Chart.js@v2.9.3...v2.9.4)

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

web-ui/package-lock.json

@@ -49,7 +49,7 @@
     "@swimlane/ngx-charts": "^14.0.0",
     "angular2-chartjs": "0.4.1",
     "bootstrap": "4.3.1",
-    "chart.js": "2.7.1",
+    "chart.js": "2.9.4",
     "ckeditor": "4.7.3",
     "classlist.js": "1.1.20150312",
     "core-js": "2.5.1",