fix: gatsby swag revival

updated data.json for 'gatsby' swag, which was marked as 'expired'.

- updated the swag link
- removed 'expired' tag

data.json

@@ -426,10 +426,10 @@
     "name": "Gatsby",
     "difficulty": "hard",
     "description": "Get a pull request merged into Gatsby and receive a free shirt, socks, or stickers.",
-    "reference": "https://www.gatsbyjs.org/docs/contributor-swag/",
+    "reference": "https://www.gatsbyjs.com/contributing/contributor-swag/",
     "image": "https://i.imgur.com/e7GwaTN.png",
     "dateAdded": "2018-10-24T11:42:09.000Z",
-    "tags": ["clothing", "stickers", "expired"]
+    "tags": ["clothing", "stickers"]
   },
   {
     "name": "GeeksForGeeks",