Eliminate use of deprecated `componentWillReceiveProps` method

See FYI

It can only happen on a new major release. The plan is to plan before just throwing the switch on React 17. In the interim, between now and a stripes-connect rewrite, the console noise is not telling us anything we don't already know, just repeating over and over "stripes-connect won't work with React 17 unless you change it".

But that will mean that when the React people actually remove the currently-deprecated lifecycle methods, stripes-connect will straight-up stop working. Is the plan to suddenly do the rewrite in a panic then?

At this point, we should consider renaming cWRP with the UNSAFE_ prefix in order to avoid the console warnings now issues about this long-deprecated function. This refactor would be a huge refactor.