Fix button docs

docs/_data/blog/migratingv070.json

@@ -32,7 +32,7 @@
       "changes": [
         {
           "variable": "$hr-background-color",
-          "from": "border",
+          "from": "$border",
           "to": "$background"
         },
         {
@@ -42,6 +42,16 @@
         }
       ]
     },
+    {
+      "file": "sass/elements/content.sass",
+      "changes": [
+        {
+          "variable": "$content-heading-weight",
+          "from": "$weight-normal",
+          "to": "$weight-semibold"
+        }
+      ]
+    },
     {
       "file": "sass/components/message.sass",
       "changes": [