Fix PDF build for Python 3.14 #788

Job	Run time
sync / sync	1m 1s
check / Check for zero-width space characters	8s
check / Build docs (epub)	6m 43s
check / Build docs (html)	7m 10s
check / Build docs (latex)	7m 8s
check / Lint translations	35s
check / Build docs (pdf)	10m 53s
	33m 38s

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