[skara] RFR: Move hgupdate-sync label functionality to SyncLabelBot [v2]

[Robin Westberg]

> Move the responsibility of updating the hgupdate-sync label to the SyncLabelBot.

Robin Westberg has updated the pull request incrementally with one additional commit since the last revision:

  Rename work item class

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Changes:
  - all: https://git.openjdk.java.net/skara/pull/1021/files
  - new: https://git.openjdk.java.net/skara/pull/1021/files/c60e5f3a..3a546c49

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=skara&pr=1021&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=skara&pr=1021&range=00-01

  Stats: 6 lines in 2 files changed: 0 ins; 0 del; 6 mod
  Patch: https://git.openjdk.java.net/skara/pull/1021.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/1021/head:pull/1021

PR: https://git.openjdk.java.net/skara/pull/1021