RFR: 8344080: Return type mismatch for jfr_unregister_stack_filter

[Markus Grönlund]

Greetings,

Tiny adjustment to function declaration.

Test: jdk_jfr

Thanks
Markus

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Commit messages:
 - 8344080

Changes: https://git.openjdk.org/jdk/pull/22068/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=22068&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8344080
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/22068.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/22068/head:pull/22068

PR: https://git.openjdk.org/jdk/pull/22068