deps: Upgrade ESLint-related deps to their latest.

Done with

```
yarn upgrade --latest $(tools/test deps | grep eslint)
```

which was easier than 01593b3.

One thing we neglected to mention in 01593b3, which still applies
here, is that the version of ESLint used by `prettier-eslint-cli` is
still 5, and it's unclear when (or if) that'll change [1], which is
unfortunate.

[1] prettier/prettier-eslint-cli#304

package.json

@@ -106,16 +106,16 @@
     "babel-plugin-transform-remove-console": "^6.9.4",
     "core-js": "^3.1.4",
     "deep-freeze": "^0.0.1",
-    "eslint": "^6.8.0",
-    "eslint-config-airbnb": "^18.2.0",
-    "eslint-config-prettier": "^6.11.0",
-    "eslint-plugin-flowtype": "^4.7.0",
-    "eslint-plugin-import": "^2.22.0",
-    "eslint-plugin-jest": "^23.20.0",
-    "eslint-plugin-jsx-a11y": "^6.3.1",
-    "eslint-plugin-prettier": "^3.1.4",
-    "eslint-plugin-react": "^7.20.5",
-    "eslint-plugin-react-hooks": "^4.0.8",
+    "eslint": "^7.14.0",
+    "eslint-config-airbnb": "^18.2.1",
+    "eslint-config-prettier": "^6.15.0",
+    "eslint-plugin-flowtype": "^5.2.0",
+    "eslint-plugin-import": "^2.22.1",
+    "eslint-plugin-jest": "^24.1.3",
+    "eslint-plugin-jsx-a11y": "^6.4.1",
+    "eslint-plugin-prettier": "^3.2.0",
+    "eslint-plugin-react": "^7.21.5",
+    "eslint-plugin-react-hooks": "^4.2.0",
     "flow-bin": "^0.113.0",
     "flow-coverage-report": "^0.6.0",
     "flow-typed": "^2.4.0",
@@ -129,7 +129,7 @@
     "lolex": "^5.1.1",
     "metro-react-native-babel-preset": "^0.63.0",
     "prettier": "^1.18.2",
-    "prettier-eslint": "^11.0.0",
+    "prettier-eslint": "^12.0.0",
     "prettier-eslint-cli": "^5.0.0",
     "prop-types": "^15.7.2",
     "react-dom": "16.11.0",