RFR: 7435: Update the maven enforcer plugin

[Patrick Reinhart]

Signed-off-by: Patrick Reinhart <patrick at reini.net>

Use latest released final version.

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Commit messages:
 - 7435: Update the maven enforcer plugin

Changes: https://git.openjdk.java.net/jmc/pull/327/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jmc&pr=327&range=00
  Issue: https://bugs.openjdk.java.net/browse/JMC-7435
  Stats: 3 lines in 3 files changed: 0 ins; 0 del; 3 mod
  Patch: https://git.openjdk.java.net/jmc/pull/327.diff
  Fetch: git fetch https://git.openjdk.java.net/jmc pull/327/head:pull/327

PR: https://git.openjdk.java.net/jmc/pull/327