Reset CHANGELOG.md (#5239)

## Motivation
Prepare `CHANGELOG.md` for next release

## Changes
- add unreleased section

## Test Plan
- n/a

## TODO
<!-- This section should be removed when all items are complete -->
- [x] Explain motivation or link existing issue(s)
- [x] Test changes and document test plan
- [x] Update documentation as needed
- [x] Update [changelog](../CHANGELOG.md) as needed

CHANGELOG.md

@@ -2,6 +2,16 @@
 
 See [RELEASE](./RELEASE.md) for workflow instructions.
 
+## UNRELEASED
+
+### Upgrade information
+
+### Highlights
+
+### Features
+
+### Improvements
+
 ## 1.3.0
 
 ### Upgrade information

RELEASE.md

@@ -2,15 +2,15 @@
 
 ## Releasing a major version
 
-Rename UNRELEASED to a concrete <version> and create a PR with commit: Release <version>.
-Branch name should match the <version> set in CHANGELOG.
+Rename UNRELEASED to a concrete `version` and create a PR with commit: Release `version`.
+Branch name should match the `version` set in CHANGELOG.
 Additionally tag that same commit with 0 as a patch version (if branch is v1.1 - tag is v1.1.0).
 
 ## Releasing a minor version
 
 ### Latest
 
-Rename UNRELEASED to a concrete <version>. If previous major was v1.1.0, new version will
+Rename UNRELEASED to a concrete `version`. If previous major was v1.1.0, new version will
 be v1.1.1.
 Commit changes, create pr, and create a tag.
 Rebase released branch onto develop.
@@ -21,7 +21,7 @@ This is a simplified workflow to avoid cherry-picks and maintaining changelog in
 
 Cherry-pick selected commits to major release branch.
 Copy selected commits to CHANGELOG.md.
-Rename UNRELEASED to a concrete <version>.
+Rename UNRELEASED to a concrete `version`.
 Commit changes, and create a tag.
 
 ## Preparing for next release