Unskip reactjs-sample in marketplace.ini, fixing random test failures

reactjs-sample-tests.run-tests:
[INFO]      [exec] > nuxeo_app@1.0.0 test /opt/jenkins/workspace/Deploy/IT-nuxeo-master-build/nuxeo/marketplace/reactjs-sample-ui/reactjs-sample-ftest
[INFO]      [exec] > wdio wdio.conf.js
[INFO]      [exec] ․․F
[INFO]      [exec] 2 passing (22.50s)
[INFO]      [exec] 1 failing
[INFO]      [exec] 1) Navigate to Sample UI should be on the Sample UI page:
[INFO]      [exec] An element could not be located on the page using the given search parameters (".side-panel-profile").
[INFO]      [exec] running chrome
[INFO]      [exec] Error: An element could not be located on the page using the given search parameters (".side-panel-profile").
[INFO]      [exec]     at Promise.F (node_modules/core-js/library/modules/_export.js:35:28)
[INFO]      [exec]     at getText() - at Context.<anonymous> (tests/specs/test-login.js:57:26)
[INFO]      [exec] Wrote xunit report to [./junit_report].
[INFO]      [exec] npm ERR! Test failed.  See above for more details.