f grammar, i guess

Author: TheBlueMatt

CONTRIBUTING.md

@@ -101,7 +101,7 @@ don't hesitate to ask if the assigned party or previous commenters are still
 working on it if it has been awhile.
 
 Any changes that have nontrivial backwards compatibility considerations should
-have an entry added in the `pending_changelog` folder that includes the
+have an entry added in the `pending_changelog` folder which includes the
 CHANGELOG entries that should be added in the next release.
 
 Peer review