Fix checkboxes in PR template

.github/pull_request_template.md

@@ -1,10 +1,10 @@
 <!-- Please tick if the following things apply. You… -->
 
-- [] read the [CONTRIBUTING guidelines](README.md#user-content-contributing)
-- [] raised a GitHub issue or discussed it on the projects chat beforehand
-- [] added unit tests
-- [] added integration tests
-- [] updated documentation if needed
-- [] updated CHANGELOG.md
+- [ ] read the [CONTRIBUTING guidelines](README.md#user-content-contributing)
+- [ ] raised a GitHub issue or discussed it on the projects chat beforehand
+- [ ] added unit tests
+- [ ] added integration tests
+- [ ] updated documentation if needed
+- [ ] updated CHANGELOG.md
 
 <!-- If applicable, please reference the issue using `Fixes #XXX` and add tests to cover your new code. -->