RFR: 8365632: Remove unused local variable in GlassWindow

[Michael Strauß]

`originalSize` in GlassWindow::HandleNCCalcSizeEvent is not used and can be removed.

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

Commit messages:
 - Remove unused local variable

Changes: https://git.openjdk.org/jfx/pull/1872/files
  Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1872&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8365632
  Stats: 2 lines in 1 file changed: 0 ins; 1 del; 1 mod
  Patch: https://git.openjdk.org/jfx/pull/1872.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1872/head:pull/1872

PR: https://git.openjdk.org/jfx/pull/1872