Java8: Update the broken links and commands

[YOUNAVI]

When I tried to build the docker image of jdk8 from this, I found it a bit old and it includes some broken stuff like link or command. And I seek about for a new link like mirror or other substitute but I couldn't.
Finally, I made it up and actually I got the jdk8 for linux.tar.gz file for myself from the official ORACLE page since the curl link has been broken.

Here's what I changed:

1. "FROM ubuntu:lastest" -> "From ubuntu:focal-20241011" (from https://hub.docker.com/_/ubuntu/tags?name=focal)
2. add "COPY jdk8.tar.gz /" and you should get your jdk tar gz from the official ORACLE Page (https://www.oracle.com/kr/java/technologies/javase/javase8-archive-downloads.html).
3. delete "curl ...GeoTrust_Global_CA.pem ... http://download.oracle.com/"-linux-x64.tar.gz " which is not available anymore.
4. fix "tar xz -C /tmp" with "tar -xz -C /tmp -f jdk8.tar.gz" because you need to specify the file.

If you are still interesting in this traditional system, please read this and consider my log.