[jdk17u-dev] RFR: 8280820: Clean up bug8033699 and bug8075609.java tests: regtesthelpers aren't used

[Goetz Lindenmaier]

I backport this for parity with 17.0.16-oracle.

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Commit messages:
 - Backport fd8a3dcc52dc5d6b62edd83eacef5934f6294e80

Changes: https://git.openjdk.org/jdk17u-dev/pull/3350/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=3350&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8280820
  Stats: 75 lines in 2 files changed: 14 ins; 13 del; 48 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/3350.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev.git pull/3350/head:pull/3350

PR: https://git.openjdk.org/jdk17u-dev/pull/3350