fix: Dockerfile to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-DEBIAN11-OPENSSL-3368735
- https://snyk.io/vuln/SNYK-DEBIAN11-OPENSSL-5291773
- https://snyk.io/vuln/SNYK-DEBIAN11-OPENSSL-5291777
- https://snyk.io/vuln/SNYK-DEBIAN11-OPENSSL-5661566
- https://snyk.io/vuln/SNYK-DEBIAN11-OPENSSL-5661566

Dockerfile

@@ -1,5 +1,5 @@
 # REF: https://hub.docker.com/_/python
-FROM python:3.11.3-slim-bullseye
+FROM python:3-slim-bullseye
 
 LABEL "com.github.actions.name"="Spellcheck Action"
 LABEL "com.github.actions.description"="Check spelling of files in repository"