RFR: 7415: Fix Maven prerequisite in README

Mon Oct 4 09:19:18 UTC 2021

Hi,

I just noticed that the minimum Maven prerequisite is wrong in the README. CI-friendly versions like `revision` and `changelist` are a feature of `3.5.x` and thus `3.3.x` is not sufficient anymore.

I hope you can create a ticket for me and sponsor this.

Cheers,
Christoph

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Commit messages:
 - Fix Maven prerequisite in README

Changes: https://git.openjdk.java.net/jmc/pull/318/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jmc&pr=318&range=00
  Issue: https://bugs.openjdk.java.net/browse/JMC-7415
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jmc/pull/318.diff
  Fetch: git fetch https://git.openjdk.java.net/jmc pull/318/head:pull/318

PR: https://git.openjdk.java.net/jmc/pull/318