fix: Dockerfile to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-DEBIAN10-DPKG-2847944
- https://snyk.io/vuln/SNYK-DEBIAN10-FREETYPE-2774655
- https://snyk.io/vuln/SNYK-DEBIAN10-OPENSSL-2807585
- https://snyk.io/vuln/SNYK-DEBIAN10-SYSTEMD-3339153
- https://snyk.io/vuln/SNYK-DEBIAN10-SYSTEMD-3339153

Dockerfile

@@ -10,7 +10,7 @@ RUN mvn dependency:go-offline -B
 # RUN mvn package
 RUN mvn clean install package
 
-FROM openjdk:11.0.14.1-jre-buster
+FROM openjdk:11.0.15-jre-buster
 # Add the service itself
 COPY --from=maven  target/hell-on-world-rest-*.jar /usr/share/javalin/