fix: Dockerfile to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-ALPINE314-EXPAT-2342147
- https://snyk.io/vuln/SNYK-ALPINE314-EXPAT-2342148
- https://snyk.io/vuln/SNYK-ALPINE314-EXPAT-2342152
- https://snyk.io/vuln/SNYK-ALPINE314-EXPAT-2342153
- https://snyk.io/vuln/SNYK-ALPINE314-EXPAT-2342154

Dockerfile

@@ -2,7 +2,7 @@ ARG GIT_COMMIT=unspecified
 ARG GIT_REMOTE=unspecified
 ARG VERSION=unspecified
 
-FROM python:3.9.8-alpine
+FROM python:3.9-alpine
 
 ARG GIT_COMMIT
 ARG GIT_REMOTE