Update ITImagetool.java

Author: rjeberhard

tests/src/test/java/com/oracle/weblogic/imagetool/tests/ITImagetool.java

@@ -965,7 +965,7 @@ void createMiiOl8slim(TestInfo testInfo) throws Exception {
             String tagName = build_tag + ":" + getMethodName(testInfo);
             String command = new CreateCommand()
                 .tag(tagName)
-                .fromImage("ghcr.io/oracle/oraclelinux", "7-slim")
+                .fromImage("ghcr.io/oracle/oraclelinux", "8-slim")
                 .version(WLS_VERSION)
                 .wdtVersion(WDT_VERSION)
                 .wdtArchive(WDT_ARCHIVE)