chore(deps): update dependency eslint to ^7.21.0

Author: renovate-bot

package.json

@@ -26,7 +26,7 @@
     "@sourcegraph/eslint-config": "^0.22.0",
     "@sourcegraph/prettierrc": "^3.0.3",
     "@sourcegraph/tsconfig": "^4.0.1",
-    "eslint": "^7.20.0",
+    "eslint": "^7.21.0",
     "husky": "^5.0.9",
     "prettier": "^2.2.1",
     "semantic-release": "^17.3.9",