RFR: 8368576: PrintJob.getGraphics() does not specify behavior after PrintJob.end()

[Phil Race]

Update the spec. of java.awt.PrintJob.getGraphics() to document long standing behaviour after PrintJob.end() has been called.

A CSR has been created https://bugs.openjdk.org/browse/JDK-8368577

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Commit messages:
 - 8368576

Changes: https://git.openjdk.org/jdk/pull/27474/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=27474&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8368576
  Stats: 2 lines in 1 file changed: 2 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/27474.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27474/head:pull/27474

PR: https://git.openjdk.org/jdk/pull/27474