Pluralize "announcement" tag to match the other posts

Author: hasparus

src/pages/blog/2025-09-08-announcing-graphqldotorg.md

@@ -1,6 +1,6 @@
 ---
 title: "Introducing the New GraphQL.org: A Decade of Evolution, Redesigned"
-tags: ["announcement"]
+tags: ["announcements"]
 date: 2025-09-08
 byline: Saihajpreet Singh & Piotr Monwid-Olechnowicz
 ---