RFR: 8353002: Remove unnecessary Windows version check in WTaskbarPeer

[Daniel Gredler]

WTaskbarPeer contains a check as to whether the current Windows version is Windows 7 or later. The current minimum supported version is Windows 10, so this is no longer needed.

There didn't seem to be a public test exercising this code, so I also added a basic Taskbar sanity test.

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Commit messages:
 - Remove unnecessary Windows version check in WTaskbarPeer

Changes: https://git.openjdk.org/jdk/pull/24287/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=24287&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8353002
  Stats: 55 lines in 2 files changed: 50 ins; 3 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/24287.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/24287/head:pull/24287

PR: https://git.openjdk.org/jdk/pull/24287