RFR: 8072: Bump some maven plugins and fix warnings

[Christoph Langer]

Current maven build of JMC core shows some warnings/validation errors that can be fixed by bumping plugin versions.

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Commit messages:
 - JMC-8072

Changes: https://git.openjdk.org/jmc/pull/486/files
 Webrev: https://webrevs.openjdk.org/?repo=jmc&pr=486&range=00
  Issue: https://bugs.openjdk.org/browse/JMC-8072
  Stats: 40 lines in 1 file changed: 22 ins; 15 del; 3 mod
  Patch: https://git.openjdk.org/jmc/pull/486.diff
  Fetch: git fetch https://git.openjdk.org/jmc.git pull/486/head:pull/486

PR: https://git.openjdk.org/jmc/pull/486