RFR: 8371681: Remove unused VMOp type CollectForCodeCacheAllocation

[Axel Boldt-Christmas]

The VMOp type `CollectForCodeCacheAllocation` was added with [JDK-8284161](https://bugs.openjdk.org/browse/JDK-8284161) but was never used. More than likely this is some vestigial part from earlier iterations of the Loom project.

I suggest a trivial removal of this unused symbol.

* Testing
   * GHA

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Commit messages:
 - 8371681: Remove unused VMOp type CollectForCodeCacheAllocation

Changes: https://git.openjdk.org/jdk/pull/28256/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=28256&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8371681
  Stats: 1 line in 1 file changed: 0 ins; 1 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/28256.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28256/head:pull/28256

PR: https://git.openjdk.org/jdk/pull/28256