Fix generation of multiple bibliography sections #20662

Job	Run time
CHANGELOG.md - only unreleased touched	16s
CHANGELOG.md	8s
Checkstyle	2m 28s
Code coverage	27s
Database tests	2m 49s
Validate Gradle Wrapper	8s
GUI tests	1m 33s
Markdown	8s
Find merge conflicts	4s
Modernizer	1m 13s
OpenRewrite	2m 9s
Source branch is other than "main"	2s
Validate requirement coverage	30s
Unit tests	6m 59s
upload-pr-number	4s
	18m 58s

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