Update Dockerfile description for JDK 17

closes jboss-dockerfiles#194

Dockerfile

@@ -1,12 +1,12 @@
-# By default, build on JDK 17 on CentOS 7.
+# By default, build on JDK 17 on UBI 9.
 ARG jdk=21
 # Red Hat UBI 9 (ubi9-minimal) should be used on JDK 20 and later.
 ARG dist=ubi9-minimal
 FROM eclipse-temurin:${jdk}-${dist}
 
 LABEL org.opencontainers.image.source=https://github.com/jboss-dockerfiles/wildfly org.opencontainers.image.title=wildfly org.opencontainers.imag.url=https://github.com/jboss-dockerfiles/wildfly org.opencontainers.image.vendor=WildFly
 
-# Starting on jdk 21 eclipse-temurin is based on ubi9-minimal version 9.3 
+# Starting on jdk 17 eclipse-temurin is based on ubi9-minimal version 9.3 
 #   that doesn't includes shadow-utils package that provides groupadd & useradd commands
 # Conditional RUN: IF no groupadd AND microdnf THEN: update, install shadow-utils, clean
 RUN if ! [ -x "$(command -v groupadd)" ] && [ -x "$(command -v microdnf)" ]; then microdnf update -y && microdnf install --best --nodocs -y shadow-utils && microdnf clean all; fi