RFR: 8327289: Remove unused PrintMethodFlushingStatistics option

[Coleen Phillimore]

On Mon, 22 Apr 2024 20:09:47 GMT, Sonia Zaldana Calles <szaldana at openjdk.org> wrote:

> Hi all, 
> 
> This PR removes the option ```PrintMethodFlushingStatistics```. Last usage was removed in [8290025](https://bugs.openjdk.org/browse/JDK-8290025). 
> 
> Testing: 
> - [x] Verified unrecognized VM option gets reported after patch. 
> 
> Thanks, 
> Sonia

This is a Diagnostic flag so doesn't need a CSR.

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PR Comment: https://git.openjdk.org/jdk/pull/18903#issuecomment-2073052888