RFR: 8324543: Remove Space::object_iterate

[Albert Mingkun Yang]

Trivial removing effectively dead code.

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Commit messages:
 - trivial

Changes: https://git.openjdk.org/jdk/pull/17539/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=17539&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8324543
  Stats: 6 lines in 1 file changed: 0 ins; 5 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/17539.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/17539/head:pull/17539

PR: https://git.openjdk.org/jdk/pull/17539