Fix "yntax" typo in jekyll.json (#4082)

Author: mattxwang

src/schemas/json/jekyll.json

@@ -586,7 +586,7 @@
       "minLength": 1
     },
     "highlighter": {
-      "description": "A yntax highlighter for the current site\nhttps://jekyllrb.com/docs/configuration/default/",
+      "description": "A syntax highlighter for the current site\nhttps://jekyllrb.com/docs/configuration/default/",
       "type": "string",
       "default": "rouge",
       "minLength": 1