RFR: Allow committers to review Shenandoah changes

[Roman Kennke]

We shouldn't need formal distinction between reviewers and commiters in Shenandoah. I propose to allow all committers to also review changes.

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Commit messages:
 - Allow committers to review Shenandoah changes

Changes: https://git.openjdk.java.net/shenandoah/pull/45/files
 Webrev: https://webrevs.openjdk.java.net/?repo=shenandoah&pr=45&range=00
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/shenandoah/pull/45.diff
  Fetch: git fetch https://git.openjdk.java.net/shenandoah pull/45/head:pull/45

PR: https://git.openjdk.java.net/shenandoah/pull/45