Update Changelog template (#24214)

## Summary & Motivation

As title. Leaving the below sections unaltered to illustrate.

This workflow for selecting a category is a bit easier / more obvious.

## How I Tested These Changes

## Changelog

NOCHANGELOG

- [ ] `NEW` _(added new feature or capability)_
- [ ] `BUGFIX` _(fixed a bug)_
- [ ] `DOCS` _(added or updated documentation)_

.github/PULL_REQUEST_TEMPLATE.md

@@ -2,6 +2,10 @@
 
 ## How I Tested These Changes
 
-## Changelog [New | Bug | Docs]
+## Changelog
 
-> Replace this message with a changelog entry, or `NOCHANGELOG`
+Insert changelog entry or "NOCHANGELOG" here.
+
+- [ ] `NEW` _(added new feature or capability)_
+- [ ] `BUGFIX` _(fixed a bug)_
+- [ ] `DOCS` _(added or updated documentation)_