RFR: 8273357: SecurityManager deprecation warning from java/awt/regtesthelpers/Util.java

[Phil Race]

The compilation of a number of tests that use regtesthelpers/Util.java are getting a warning about
the deprecation-for-removal of the SecurityManager.
This suppresses that warning.

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Commit messages:
 - 8273357

Changes: https://git.openjdk.org/jdk/pull/11492/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=11492&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8273357
  Stats: 1 line in 1 file changed: 1 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/11492.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11492/head:pull/11492

PR: https://git.openjdk.org/jdk/pull/11492