fix: backend/Dockerfile.conformance to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-ALPINE39-OPENSSL-1089231
- https://snyk.io/vuln/SNYK-ALPINE39-OPENSSL-1089231
- https://snyk.io/vuln/SNYK-ALPINE39-OPENSSL-1089232
- https://snyk.io/vuln/SNYK-ALPINE39-OPENSSL-1089232
- https://snyk.io/vuln/SNYK-ALPINE39-OPENSSL-1089235

Author: snyk-bot

backend/Dockerfile.conformance

@@ -40,7 +40,7 @@ RUN chmod +x /test/integration/run.sh
 RUN tar -czvf /test.tar.gz /test
 
 
-FROM alpine:3.9
+FROM alpine:3.18.12
 
 COPY --from=builder /test.tar.gz /
 RUN tar -xzvf /test.tar.gz