RFR: 1729: CSR bot should not remove CSR label if one of the CSR issues is withdrawn

[Zhao Song]

While testing [SKARA-1714](https://bugs.openjdk.org/browse/SKARA-1714), I discovered a bug in the PullRequestWorkItem of the CSR bot. 

Currently, the CSR bot would remove CSR label if all the CSR issues of the pr is closed(whether approved or withdrawn). However, this behavior does not align with the original logic. The correct logic is that if one of the CSR issues is withdrawn, CSR bot should not remove the CSR label automatically. In this case, only reviewer uses '/csr unneeded' command will be able to remove the CSR label.

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Commit messages:
 - SKARA-1729

Changes: https://git.openjdk.org/skara/pull/1451/files
 Webrev: https://webrevs.openjdk.org/?repo=skara&pr=1451&range=00
  Issue: https://bugs.openjdk.org/browse/SKARA-1729
  Stats: 12 lines in 2 files changed: 8 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/skara/pull/1451.diff
  Fetch: git fetch https://git.openjdk.org/skara pull/1451/head:pull/1451

PR: https://git.openjdk.org/skara/pull/1451