RFR: JDK-8307123: Fix deprecation warnings in DPrinter

[Jonathan Gibbons]

Please review a trivial test clean to fix some deprecation warnings in the test/langtools DPrinter class.

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Commit messages:
 - JDK-8307123: Fix deprecation warnings in DPrinter

Changes: https://git.openjdk.org/jdk/pull/13747/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13747&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8307123
  Stats: 2 lines in 1 file changed: 2 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/13747.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13747/head:pull/13747

PR: https://git.openjdk.org/jdk/pull/13747