RFR: 8308875: java/awt/Toolkit/GetScreenInsetsCustomGC/GetScreenInsetsCustomGC.java failed with 'Cannot invoke "sun.awt.X11GraphicsDevice.getInsets()" because "device" is null'

[Maxim Kartashev]

8308875 is a regression after the recent [fix for 8305578](https://github.com/openjdk/jdk/commit/d7245f70) that effectively undid a part of [another, older, change](https://github.com/openjdk/jdk/commit/40f6d697d25293282e3d3ee695ef8cd9a5494799), the one made to fix [8233573](https://bugs.openjdk.org/browse/JDK-8233573).

This commits brings that part back and passes the test `java/awt/Toolkit/GetScreenInsetsCustomGC/GetScreenInsetsCustomGC.java` on Linux, so the test is also removed from the ProblemList file.

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Commit messages:
 - 8308875: java/awt/Toolkit/GetScreenInsetsCustomGC/GetScreenInsetsCustomGC.java failed with 'Cannot invoke "sun.awt.X11GraphicsDevice.getInsets()" because "device" is null'

Changes: https://git.openjdk.org/jdk/pull/14170/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=14170&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8308875
  Stats: 15 lines in 2 files changed: 5 ins; 2 del; 8 mod
  Patch: https://git.openjdk.org/jdk/pull/14170.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14170/head:pull/14170

PR: https://git.openjdk.org/jdk/pull/14170