Update apache airflow version (#3998)

**Description**
Updating the apache airflow version
to fix the vulnerability.

Author: sthodimi

requirements/extras/test_requirements.txt

@@ -12,7 +12,7 @@ awslogs==0.14.0
 black==22.3.0
 stopit==1.1.2
 # Update tox.ini to have correct version of airflow constraints file
-apache-airflow==2.6.0
+apache-airflow==2.6.3
 apache-airflow-providers-amazon==7.2.1
 attrs>=23.1.0,<24
 fabric==2.6.0