message: fix(splunk-on-call-plugin): remove date-fns dependency
diff: "@material-ui/icons": "^4.9.1",
  "@material-ui/lab": "4.0.0-alpha.45",
  "classnames": "^2.2.6",
  - "date-fns": "^2.15.0",
  "luxon": "^1.25.0",
  "react": "^16.13.1",
  "react-dom": "^16.13.1",
  