RFR: 8328540: test javax/swing/JSplitPane/4885629/bug4885629.java fails on windows hidpi

[Phil Race]

A simple fix to the test to skip sampling the leftmost and rightmost ends of the divider
to avoid possible issues at fractional scales.

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Commit messages:
 - 8328540

Changes: https://git.openjdk.org/jdk/pull/18384/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=18384&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8328540
  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/18384.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18384/head:pull/18384

PR: https://git.openjdk.org/jdk/pull/18384