RFR: 8320602: Lock contention in SchemaDVFactory.getInstance()

[Iris Clark]

On Mon, 27 Nov 2023 17:24:35 GMT, Joe Wang <joehw at openjdk.org> wrote:

> Applying an update from the upstream source, quote: "Removing synchronized from the getInstance() methods". As the reporter noted, this change was made 16 years ago.
> 
> Tests: SQE & unit tests passed

Verified `synchronized` keyword removed from method declaration as in upstream source.

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Marked as reviewed by iris (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/16829#pullrequestreview-1751076242