<Swing Dev> RFR: 7190589: [macosx] In the test bug4278839 never press ctrl+arrow

[Sergey Bylokhov]

After one of the fixes in the bug4278839.java test, Yuri(@yan-too) suggested that the check for the Aqua L&F should be updated to check the macOS instead. That code was needed to move the cursor to the beginning of the test, but since then another fix was integrated:
https://hg.openjdk.java.net/jdk/jdk/rev/9db62a092725
The "area.setCaretPosition(0);" has the same purpose and the old code became useless and can be removed.

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

Commit messages:
 - Update bug4278839.java

Changes: https://git.openjdk.java.net/jdk/pull/848/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=848&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-7190589
  Stats: 8 lines in 1 file changed: 1 ins; 6 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/848.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/848/head:pull/848

PR: https://git.openjdk.java.net/jdk/pull/848