RFR: 8348865: JButton/bug4796987.java never runs because Windows XP is unavailable [v2]

[Alexey Ivanov]

> The `javax/swing/JButton/4796987/bug4796987.java` test strictly verifies if it's run on Windows XP, for this reason it never runs on modern versions of Windows.
> 
> Since Windows XP is obsolete and visual styles cannot be disabled since Windows 8, I removed the OS version check completely.
> 
> I captured an image of the panel and analyse colors in the image instead of using `Robot.getPixelColor`; I save the image for reference if the test fails.
> 
> The updated test passes in the CI.

Alexey Ivanov has updated the pull request incrementally with two additional commits since the last revision:

 - Update the test summary
 - Remove the redundant button

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/23336/files
  - new: https://git.openjdk.org/jdk/pull/23336/files/62833cbc..0349f37a

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=23336&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=23336&range=00-01

  Stats: 5 lines in 1 file changed: 1 ins; 3 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/23336.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23336/head:pull/23336

PR: https://git.openjdk.org/jdk/pull/23336