pdf: update year to 2026 in copyright.tex (#3042) #8176

Job	Run time
check-unclosed-tags	9s
markdownlint	25s
verify-internal-links	28s
check-git-conflicts	8s
check-manual-line-breaks	9s
check-control-characters	10s
verify-internal-link-anchors	16s
check-file-encoding	12s
	1m 57s

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