actually fix the github-actions manager not knowing how to find coastalcommits actions

oops, definitely didn't put this in the wrong file the first time around

default.json

@@ -10,6 +10,17 @@
     {
       "matchUpdateTypes": ["digest"],
       "automerge": true
+    },
+    {
+      "matchPackageNames": [
+        "/^actions\\//"
+      ],
+      "matchManagers": [
+        "github-actions"
+      ],
+      "registryUrls": [
+        "https://c.csw.im"
+      ]
     }
   ]
 }