fix: docker/Dockerfile to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-DEBIAN10-OPENSSL-3314585
- https://snyk.io/vuln/SNYK-DEBIAN10-OPENSSL-3314606
- https://snyk.io/vuln/SNYK-DEBIAN10-OPENSSL-3314607
- https://snyk.io/vuln/SNYK-DEBIAN10-OPENSSL-3368736
- https://snyk.io/vuln/SNYK-DEBIAN10-OPENSSL-5661563

docker/Dockerfile

@@ -1,4 +1,4 @@
-FROM python:3.11.1-slim-buster
+FROM python:3-slim-buster
 WORKDIR /app
 ENV PIP_NO_CACHE_DIR=off
 ENV PYTHONUNBUFFERED=1