grammar in pull request template

Author: chayim

.github/PULL_REQUEST_TEMPLATE.md

@@ -7,7 +7,7 @@ _Please make sure to review and check all of these items:_
 - [ ] Is the new or changed code fully tested?
 - [ ] Is a documentation update included (if this change modifies existing APIs, or introduces new ones)?
 - [ ] Is there an example added to the examples folder (if applicable)?
-- [ ] Is the changes added to CHANGES file?
+- [ ] Was the change added to CHANGES file?
 
 _NOTE: these things are not required to open a PR and can be done
 afterwards / while the PR is open._