Building the documentation fails with newly released blurb 2.0

[vstinner]

Bug report

Bug description:

Example of failure: https://github.com/python/cpython/actions/runs/12789465122/job/35652975974?pr=128868

blurb.blurb.BlurbError: Error in Misc/NEWS.d/3.11.0b1.rst:581:
'gh-issue:' or 'bpo:' must be specified in the metadata

CPython versions tested on:

CPython main branch

Operating systems tested on:

Linux

Linked PRs

• gh-128874: Fix the documentation for blurb 2.0 #128875
• [3.13] gh-128874: Fix the documentation for blurb 2.0 (GH-128875) #128877
• [3.12] gh-128874: Fix the documentation for blurb 2.0 (GH-128875) #128878
• [3.11] gh-128874: Fix the documentation for blurb 2.0 (GH-128875) #128879
• [3.10] gh-128874: Fix the documentation for blurb 2.0 (#128875) #128890