RFR: 8256663: [test] Deprecated use of new Double in jshell ImportTest

[Roger Riggs]

The jep-390 warnings caused a couple of tests to fail.
Suppressing the warnings to re-enable the tests.

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Commit messages:
 - Fix tests broken by new warnings

Changes: https://git.openjdk.java.net/valhalla/pull/270/files
 Webrev: https://webrevs.openjdk.java.net/?repo=valhalla&pr=270&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8256663
  Stats: 3 lines in 2 files changed: 0 ins; 0 del; 3 mod
  Patch: https://git.openjdk.java.net/valhalla/pull/270.diff
  Fetch: git fetch https://git.openjdk.java.net/valhalla pull/270/head:pull/270

PR: https://git.openjdk.java.net/valhalla/pull/270