Remove the CLA section of CONTRIBUTING.md (#243)
Remove the CLA section of CONTRIBUTING.md (#243)

Per https://github.com/w3c/wptdashboard/issues/118#issuecomment-330689900

The guidance around copyright headers is still in need of updating.
GoogleChrome/wptdashboard,GoogleChrome/wptdashboard,GoogleChrome/wptdashboard