RFR: 8306431: The documentation of File.listRoots should be modifid after JDK-8208077

[Nagata-Haruhito]

On Wed, 19 Apr 2023 07:34:30 GMT, Nagata-Haruhito <duke at openjdk.org> wrote:

> I fixed File.listRoots description.
> * remove "the insertion or ejection of removable media"
> * change "available" to "existing"
> 
> Please review this change.

Thanks for your comment.

I added @implNote and moved descriptions.

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PR Comment: https://git.openjdk.org/jdk/pull/13526#issuecomment-1515638732