RFR: 8348172: C2: Remove unused local variables in filter_helper() methods

[Marc Chevalier]

Remove useless locals from `TypeOopPtr::filter_helper` and `TypeKlassPtr::filter_helper`. There were no side effects in their init, so it's fine to remove them.

Thanks,
Marc

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Commit messages:
 - ci?
 - Remove unused locals

Changes: https://git.openjdk.org/jdk/pull/23629/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=23629&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8348172
  Stats: 4 lines in 1 file changed: 0 ins; 4 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/23629.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23629/head:pull/23629

PR: https://git.openjdk.org/jdk/pull/23629