Update Jest's own dependency on the eslint plugin (#4424)

Author: SimenB

package.json

@@ -29,7 +29,7 @@
     "eslint-plugin-babel": "^4.1.1",
     "eslint-plugin-flowtype": "^2.35.0",
     "eslint-plugin-import": "^2.6.0",
-    "eslint-plugin-jest": "^20.0.3",
+    "eslint-plugin-jest": "^21.0.0",
     "eslint-plugin-jsx-a11y": "^6.0.2",
     "eslint-plugin-markdown": "^1.0.0-beta.6",
     "eslint-plugin-prettier": "^2.1.2",

yarn.lock

@@ -3666,6 +3666,10 @@ jasmine-reporters@^2.2.0:
     mkdirp "^0.5.1"
     xmldom "^0.1.22"
 
+jest-docblock@^20.0.1:
+  version "20.0.3"
+  resolved "https://registry.yarnpkg.com/jest-docblock/-/jest-docblock-20.0.3.tgz#17bea984342cc33d83c50fbe1545ea0efaa44712"
+
 jodid25519@^1.0.0:
   version "1.0.2"
   resolved "https://registry.yarnpkg.com/jodid25519/-/jodid25519-1.0.2.tgz#06d4912255093419477d425633606e0e90782967"