RFR: 7415: Fix Maven prerequisite in README

[Marcus Hirt]

On Mon, 4 Oct 2021 09:08:09 GMT, Christoph Dreis <github.com+6304496+dreis2211 at openjdk.org> wrote:

> 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

Marked as reviewed by hirt (Lead).

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