RFR: 7191: The release notes tool should be using JDK 8

[Marcus Hirt]

Right now the launcher will not work out of the box.

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Commit messages:
 - 7191: The release notes tool should be using JDK 8

Changes: https://git.openjdk.java.net/jmc/pull/229/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jmc&pr=229&range=00
  Issue: https://bugs.openjdk.java.net/browse/JMC-7191
  Stats: 17 lines in 2 files changed: 17 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jmc/pull/229.diff
  Fetch: git fetch https://git.openjdk.java.net/jmc pull/229/head:pull/229

PR: https://git.openjdk.java.net/jmc/pull/229