RFR: 8332849: Update doc/testing.{md,html} (spelling and stale information)

[Erik Joelsson]

On Thu, 23 May 2024 23:22:51 GMT, Mikael Vidstedt <mikael at openjdk.org> wrote:

> Update the testing doc to remove some stale information (AOT_MODULES, removed in [JDK-8264805](https://bugs.openjdk.org/browse/JDK-8264805)) and fix some spelling issues.
> 
> Testing: tier1

Changes requested by erikj (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/19375#pullrequestreview-2076839326