RFR: 8325565: Remove unused SpaceClosure

[Albert Mingkun Yang]

Trivial removing dead code.

-------------

Commit messages:
 - trivial

Changes: https://git.openjdk.org/jdk/pull/17792/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=17792&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8325565
  Stats: 10 lines in 1 file changed: 0 ins; 10 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/17792.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/17792/head:pull/17792

PR: https://git.openjdk.org/jdk/pull/17792