RFR: 8257038: Remove expired flags in JDK 18

[Kim Barrett]

On Thu, 10 Jun 2021 23:15:36 GMT, David Holmes <dholmes at openjdk.org> wrote:

> Simple start of release update:
>  - remove 4 expired flags
>  - move the now obsoleted flags to the obsoleted flag section
>  - update the dummy obsoleted flag
> 
> None of the expired flags were documented so no updated needed to any docs in that regard.
> 
> Thanks,
> David

Looks good.

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Marked as reviewed by kbarrett (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/4470