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Disable version 3.9 as EOL #216

Job	Run time
sync / sync	45s
sync / commit	36s
check / Lint translations	51s
check / Build docs (latex)	8m 37s
check / Build docs (epub)	10m 5s
check / Build docs (html)	9m 57s
check / Check for zero-width space characters	7s
check / Build docs (pdf)	11m 41s
	42m 39s