[doc] Fix old release notes

do-release.sh

@@ -190,6 +190,7 @@ OLD_RELEASE_NOTES=$(tail -n +8 docs/pages/release_notes_old.md)
 OLD_RELEASE_NOTES_HEADER=$(head -n 7 docs/pages/release_notes_old.md)
 echo "${OLD_RELEASE_NOTES_HEADER}
 ${NEW_RELEASE_NOTES}
+
 ${OLD_RELEASE_NOTES}" > docs/pages/release_notes_old.md
 
 # reset release notes template

docs/pages/release_notes_old.md

@@ -87,6 +87,7 @@ No changes.
 * 74 commits
 * 18 closed tickets & PRs
 * Days since last release: 27
+
 ## 27-March-2021 - 6.33.0
 
 The PMD team is pleased to announce PMD 6.33.0.