RFR: 8329189: runtime/stack/Stack016.java fails on libgraal

[Doug Simon]

[JDK-8328858](https://bugs.openjdk.org/browse/JDK-8328858) adjusted  `depthToTry` in all `runtime/stack/Stack0*.java` tests but did so incorrectly for `Stack016.java`. The `RESERVE` value is used both to initialize `depthToTry` as well as controlling stack space to reserve for testing nested StackOverflowError handling.

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Commit messages:
 - revert RESERVE value

Changes: https://git.openjdk.org/jdk/pull/18511/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=18511&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8329189
  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/18511.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18511/head:pull/18511

PR: https://git.openjdk.org/jdk/pull/18511