RFR: 8289388: Fix warnings: method is overriding a synchronized method without being synchronized

[Kevin Rushforth]

On Fri, 8 Jul 2022 19:00:25 GMT, Andy Goryachev <angorya at openjdk.org> wrote:

> Fixes warnings generated by the latest Eclipse: 
> method is overriding a synchronized method without being synchronized

Marked as reviewed by kcr (Lead).

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PR: https://git.openjdk.org/jfx/pull/819