chore: add apache header for 2.0 changelog (apache#20713)

RELEASING/release-notes-2-0/changelog.md

@@ -1,5 +1,26 @@
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+
 ### 2.0 (Thu Jun 23 05:39:46 2022 -0600)
+
 **Database Migrations**
+
 - [#20385](https://github.com/apache/superset/pull/20385) fix(migration): Ensure key_value LargeBinary is encoded as a MEDIUMBLOB as opposed to BLOB for MySQL (@john-bodley)
 - [#20449](https://github.com/apache/superset/pull/20449) fix: RLS new db migration downgrade fails on SQLite (@dpgaspar)
 - [#20284](https://github.com/apache/superset/pull/20284) chore(migrations): Renaming migration files so that they're easier to keep track of (@craig-rueda)