fix: upgrade date-fns from 2.15.0 to 2.16.0

Snyk has created this PR to upgrade date-fns from 2.15.0 to 2.16.0.

See this package in npm:
https://www.npmjs.com/package/date-fns

See this project in Snyk:
https://app.snyk.io/org/github-newrelic/project/868cac7a-942a-4cb5-a87b-05381c8ca7ec?utm_source=github&utm_medium=upgrade-pr

package.json

@@ -10,7 +10,7 @@
     "@newrelic/gatsby-theme-newrelic": "^1.9.4",
     "@splitsoftware/splitio-react": "^1.2.0",
     "classnames": "^2.2.6",
-    "date-fns": "^2.15.0",
+    "date-fns": "^2.16.0",
     "eslint-plugin-react-hooks": "^4.1.0",
     "gatsby": "^2.24.2",
     "gatsby-image": "^2.4.14",