RFR: Fixed backing out a backport [v2]

[Jesper Wilhelmsson]

> Backing out a change was updated to not use sub-tasks, but the similar case of backing out a backport was missed.

Jesper Wilhelmsson has updated the pull request incrementally with one additional commit since the last revision:

  O to I

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Changes:
  - all: https://git.openjdk.org/guide/pull/160/files
  - new: https://git.openjdk.org/guide/pull/160/files/dedf9813..50ddd26c

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=guide&pr=160&range=01
 - incr: https://webrevs.openjdk.org/?repo=guide&pr=160&range=00-01

  Stats: 4 lines in 1 file changed: 0 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/guide/pull/160.diff
  Fetch: git fetch https://git.openjdk.org/guide.git pull/160/head:pull/160

PR: https://git.openjdk.org/guide/pull/160