Remove `ISSUE` placeholder from PR template (#35590)

.github/PULL_REQUEST_TEMPLATE.md

@@ -4,9 +4,9 @@ Thank you for contributing to this project! You must fill out the information be
 
 ### Why:
 
-Closes ISSUE
+Closes: 
 
-<!-- If there's an existing issue for your change, please replace ISSUE above with a link to the issue.
+<!-- If there's an existing issue for your change, please link to it above.
 If there's _not_ an existing issue, please open one first to make it more likely that this update will be accepted: https://github.com/github/docs/issues/new/choose. -->
 
 ### What's being changed (if available, include any code snippets, screenshots, or gifs):