fix typo

Author: i10416

_ja/index.md

@@ -37,7 +37,7 @@ scala3-sections:
         icon: "fa fa-file-text"
         link: https://dotty.epfl.ch/api/index.html
       - title: "Language Reference"
-        description: "Scala 3 の言語使用"
+        description: "Scala 3 の言語仕様"
         icon: "fa fa-book"
         link: https://dotty.epfl.ch/docs/reference/overview.html