RFR: 8236505: Mark jdk/editpad/EditPadTest.java as @headful

[Jan Lahoda]

On Thu, 16 Sep 2021 09:13:15 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> This is a GUI test, and it should be `@headful`.
> 
> Additional testing:
>  - [x] Test still runs in default, and does not run with `!headful`

Marked as reviewed by jlahoda (Reviewer).

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PR: https://git.openjdk.java.net/jdk/pull/5544