don't collect coverage in watch mode (#6326)

jest.unit.conf.json

@@ -21,7 +21,6 @@
     "ga": {},
     "document": {}
   },
-  "collectCoverage": true,
   "coverageDirectory": "./",
   "coverageReporters": ["text", "json-summary"],
   "collectCoverageFrom": ["frontend/src/**/*.js", "frontend/src/**/*.jsx"]

package.json

@@ -156,7 +156,7 @@
     "test": "yarn run test-integrated && yarn run test-unit && yarn run test-karma",
     "test-integrated": "babel-node ./frontend/test/__runner__/run_integrated_tests.js",
     "test-integrated-watch": "babel-node ./frontend/test/__runner__/run_integrated_tests.js --watch",
-    "test-unit": "jest --maxWorkers=10 --config jest.unit.conf.json",
+    "test-unit": "jest --maxWorkers=10 --config jest.unit.conf.json --coverage",
     "test-unit-watch": "jest --maxWorkers=10 --config jest.unit.conf.json --watch",
     "test-karma": "karma start frontend/test/karma.conf.js --single-run",
     "test-karma-watch": "karma start frontend/test/karma.conf.js --auto-watch --reporters nyan",