Merge duplicate spec URL

Author: caugner

css/types/attr.json

@@ -615,10 +615,7 @@
             "__compat": {
               "description": "`<transform-function>`",
               "mdn_url": "https://developer.mozilla.org/docs/Web/CSS/Reference/Values/transform-function",
-              "spec_url": [
-                "https://drafts.csswg.org/css-transforms/#transform-functions",
-                "https://drafts.csswg.org/css-transforms-2/#transform-functions"
-              ],
+              "spec_url": "https://drafts.csswg.org/css-transforms-2/#transform-functions",
               "tags": [
                 "web-features:attr"
               ],