RFR: 2201: Only fetch comments once in PullRequestWorkItem in pr bot

[Zhao Song]

On Mon, 18 Mar 2024 17:42:49 GMT, Zhao Song <zsong at openjdk.org> wrote:

> In pr bot, we are still fetching comments from the remote forge instead of using the cache after [SKARA-1709](https://bugs.openjdk.org/browse/SKARA-1709).

Thanks for the review!

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PR Comment: https://git.openjdk.org/skara/pull/1622#issuecomment-2004764213