RFR: 8289770: Drop IS_WINVISTA macro from ShellFolder2.cpp

[Tejesh R]

On Thu, 11 Apr 2024 09:33:09 GMT, Alexey Ivanov <aivanov at openjdk.org> wrote:

> This clean-up PR removes unused Windows version macro from `ShellFolder2.cpp`.
> 
> `IS_WINVISTA` was not used at all.
> 
> `IS_WINXP` guarded support for icons with alpha channel. It is now safe to assume Java runs on a Windows version later than Windows XP. Java launchers specify 6.0 as the minimum OS version which corresponds to Windows Vista.

Can you update JBS title and description regarding "support for icons with alpha channel" too. These updates are visible only in PR and not in JBS.

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PR Review: https://git.openjdk.org/jdk/pull/18736#pullrequestreview-1995873453