fix: composer/airflow_1_samples/requirements.txt to reduce vulnerabilities

The following vulnerabilities are fixed by pinning transitive dependencies:
- https://snyk.io/vuln/SNYK-PYTHON-IDNA-6597975
- https://snyk.io/vuln/SNYK-PYTHON-MARSHMALLOW-14550833

Author: snyk-bot

composer/airflow_1_samples/requirements.txt

@@ -5,3 +5,5 @@ apache-airflow-backport-providers-google==2021.3.3
 apache-airflow-backport-providers-cncf-kubernetes==2021.3.3
 kubernetes==11.0.0
 scipy==1.4.1; python_version > '3.0'
+idna>=3.7 # not directly required, pinned by Snyk to avoid a vulnerability
+marshmallow>=3.26.2 # not directly required, pinned by Snyk to avoid a vulnerability