RFR: 8359168: Revert stdin.encoding usage in test/hotspot/jtreg/vmTestbase/nsk/jvmti/AttachOnDemand/attach010/attach010Agent00.java

[Volkan Yazici]

Revert `stdin.encoding` changes to `test/hotspot/.../attach010Agent00.java` introduced in [JDK-8357993](https://bugs.openjdk.org/browse/JDK-8357993) – @plummercj [reported](https://github.com/openjdk/jdk/pull/25542#issuecomment-2950447745) that they are unnecessary.

Note that I've reset the copyright year back to 2018.

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Commit messages:
 - Revert `stdin.encoding` changes to `test/hotspot/.../attach010Agent00.java`

Changes: https://git.openjdk.org/jdk/pull/25753/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=25753&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8359168
  Stats: 3 lines in 1 file changed: 0 ins; 1 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/25753.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25753/head:pull/25753

PR: https://git.openjdk.org/jdk/pull/25753