RFR: 7903201: README.md referes old generated code pattern

Fri May 27 10:10:23 UTC 2022

On Fri, 27 May 2022 10:02:23 GMT, Athijegannathan Sundararajan <sundar at openjdk.org> wrote:

> backporting applicable parts of the same fix from jdk19. 
> 
> * using latest generated code pattern in README.md
> * using module-version in --version output

Marked as reviewed by mcimadamore (Committer).

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PR: https://git.openjdk.java.net/jextract/pull/43