RFR: 8319542: Fix boundaries of region to be tested with os::is_readable_range

[Thomas Obermeier]

PR https://github.com/openjdk/jdk/pull/16381 was already closed when it became obvious that usage of os::is_readable_range() was slightly wrong:

the " - 1" looks wrong here, because is_readable_range() checks for < to, not <= to.

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Commit messages:
 - JDK-8319542: repair boundaries to be tested

Changes: https://git.openjdk.org/jdk/pull/16676/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=16676&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8319542
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/16676.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16676/head:pull/16676

PR: https://git.openjdk.org/jdk/pull/16676