Don’t leave trailing whitespace

This is intended to be a descriptive, rather than prescriptive change; several of us appear to have our editors configured to strip trailing whitespace, and since I’m sick of seeing whitespace changes in diffs, I suggest we standardize.

I committed (and pushed!) this straight to `master` initially, suspiciously like an idiot might, hence why the commit here is a revert of a revert.
This is an example of what I am sick of seeing in diffs.