Update dependency lodash to v4.17.21

Author: renovate[bot]

notes/OVERFLOW/package.json

@@ -25,7 +25,7 @@
         "gatsby-source-filesystem": "2.3.10",
         "gatsby-transformer-remark": "2.8.14",
         "js-yaml": "3.12.2",
-        "lodash": "4.17.11",
+        "lodash": "4.17.21",
         "marked": "0.6.1",
         "moment": "2.23.0",
         "moment-strftime": "0.5.0",