[AIRFLOW-XXXX] Fix typo in tests/conftest.py (#7181)

tests/conftest.py

@@ -21,7 +21,7 @@ import sys
 
 import pytest
 
-# We should set these before loading _any_ of the rest of airlow so that the
+# We should set these before loading _any_ of the rest of airflow so that the
 # unit test mode config is set as early as possible.
 tests_directory = os.path.dirname(os.path.realpath(__file__))