Reword change log section

.github/PULL_REQUEST_TEMPLATE.md

@@ -11,7 +11,7 @@ run the test suite, write new integrations, and more.
 **Motivation:**
 <!-- What inspired you to submit this pull request? -->
 
-**Change log entry**
+**CHANGELOG entry**
 <!-- If this is a customer-visible change, a brief summary to be placed
 into the change log.
 If you are not a Datadog employee, you can skip this section