Add changelog for 2.2.3rc2

CHANGELOG.txt

@@ -1,9 +1,15 @@
-Airflow 2.2.3, 2021-12-14
+Airflow 2.2.3, 2021-12-20
 -------------------------
 
 Bug Fixes
 """""""""
 
+- Lazy Jinja2 context (#20217)
+- Exclude ``snowflake-sqlalchemy`` v1.2.5 (#20245)
+- Move away from legacy ``importlib.resources`` API (#19091)
+- Move setgid as the first command executed in forked task runner (#20040)
+- Fix race condition when starting ``DagProcessorAgent`` (#19935)
+- Limit ``httpx`` to <0.20.0 (#20218)
 - Log provider import errors as debug warnings (#20172)
 - Bump minimum required ``alembic`` version (#20153)
 - Fix log link in gantt view (#20121)
@@ -37,6 +43,7 @@ Bug Fixes
 Doc only changes
 """"""""""""""""
 
+- Warn without tracebacks when example_dags are missing deps (#20295)
 - Deferrable operators doc clarification (#20150)
 - Ensure the example DAGs are all working (#19355)
 - Updating core example DAGs to use TaskFlow API where applicable (#18562)