[docs] Improve commenting in ProcessGetData()
[docs] Improve commenting in ProcessGetData()

Summary:
This concludes backport of Core [[https://github.com/bitcoin/bitcoin/pull/18808 | PR18808]] [4/4]
https://github.com/bitcoin/bitcoin/pull/18808/commits/9847e205bf7edcac4c30ce4b6d62f482aa7bc1b7
Depends on D9085

Test Plan: `ninja`

Reviewers: #bitcoin_abc, majcosta

Reviewed By: #bitcoin_abc, majcosta

Differential Revision: https://reviews.bitcoinabc.org/D9086

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