Changed wording as @oremanj suggested

Author: Giacomo Camporini

docs/source/contributing.rst

@@ -171,9 +171,9 @@ When you are submitting your PR, you can include ``Closes #123``,
 ``Fixes: #123`` or
 `some variation <https://help.github.com/en/articles/closing-issues-using-keywords>`__
 in either your commit message or the PR description, in order to
-automatically close the issue you are solving when the PR is merged.
-This is not mandatory, but it helps cleaning up and prevents dangling issues
-that have to be closed by people coming across them in the future.
+automatically close the references issue when the PR is merged.
+This keeps us closer to the desired state where each open issue reflects some
+work that still needs to be done.
 
 
 .. _pull-request-tests: