reduce overlong line

src/bootstrap/defaults/README.md

@@ -4,7 +4,8 @@ These defaults are intended to be a good starting point for working with x.py,
 with the understanding that no one set of defaults make sense for everyone.
 
 They are still experimental, and we'd appreciate your help improving them!
-If you use a setting that's not in these defaults that you think others would benefit from, please [file an issue] or make a PR with the changes.
+If you use a setting that's not in these defaults that you think
+others would benefit from, please [file an issue] or make a PR with the changes.
 Similarly, if one of these defaults doesn't match what you use personally,
 please open an issue to get it changed.