Merge branch 'jest-run-in-band' into 'develop'

GitLab CI: try jest --runInBand

See merge request soapbox-pub/soapbox-fe!1609

.gitlab-ci.yml

@@ -57,7 +57,7 @@ lint-sass:
 
 jest:
   stage: test
-  script: yarn test:coverage
+  script: yarn test:coverage --runInBand
   only:
     changes:
       - "**/*.js"