[jdk21u-dev] RFR: 8325910: Rename jnihelper.h

[Goetz Lindenmaier]

I backport this to make later backorts clean.

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Commit messages:
 - Backport 810daf820633e16e3ab058325c539695087486d5

Changes: https://git.openjdk.org/jdk21u-dev/pull/1768/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=1768&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8325910
  Stats: 15 lines in 9 files changed: 0 ins; 0 del; 15 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/1768.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/1768/head:pull/1768

PR: https://git.openjdk.org/jdk21u-dev/pull/1768