Bump chart.js from 2.7.3 to 2.9.4

Bumps [chart.js](https://github.com/chartjs/Chart.js) from 2.7.3 to 2.9.4.
- [Release notes](https://github.com/chartjs/Chart.js/releases)
- [Commits](chartjs/Chart.js@v2.7.3...v2.9.4)

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

package.json

@@ -32,7 +32,7 @@
     "@ngrx/store": "^2.2.2",
     "@ngrx/store-devtools": "^3.2.4",
     "bootstrap": "^3.3.0",
-    "chart.js": "^2.6.0",
+    "chart.js": "^2.9.4",
     "codecov.io": "^0.1.6",
     "core-js": "^2.4.1",
     "express": "^4.16.3",