[1.8 release checklist] update citation

Author: cscheid

CITATION.cff

@@ -20,7 +20,7 @@ authors:
   given-names: "Gordon"
   orcid: "https://orcid.org/0009-0005-1809-8936"
 title: "Quarto"
-version: 1.7
+version: 1.8
 doi: 10.5281/zenodo.5960048
-date-released: 2025-04-28
+date-released: 2025-09-12
 url: "https://github.com/quarto-dev/quarto-cli"