fix: Dockerfile to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-ALPINE39-BZIP2-452847
- https://snyk.io/vuln/SNYK-ALPINE39-FREETYPE-1019627
- https://snyk.io/vuln/SNYK-ALPINE39-MUSL-458529
- https://snyk.io/vuln/SNYK-ALPINE39-MUSL-458529
- https://snyk.io/vuln/SNYK-ALPINE39-SQLITE-449671

Author: snyk-bot

Dockerfile

@@ -1,4 +1,4 @@
-FROM tomcat:8.5.40-jre8-alpine
+FROM tomcat:9.0.88-jre11
 COPY target/java-example.war /usr/local/tomcat/webapps/ROOT.war
 EXPOSE 8080
 CMD ["catalina.sh", "run"]