Deleted reference to core/admin

refs https://github.com/TryGhost/Toolbox/issues/365

- this directory no longer exists because we've brought it into the
  monorepo

ghost/core/.npmignore

@@ -45,7 +45,6 @@ core/server/lib/members/static/auth/node_modules/**
 core/built/**/*.map
 core/built/**/test-*
 core/built/**/tests-*
-core/admin/**
 test/**
 CONTRIBUTING.md
 content/themes/casper/SECURITY.md

ghost/core/jsconfig.json

@@ -7,7 +7,6 @@
      "moduleResolution": "node"
   },
   "exclude": [
-    "core/built",
-    "core/admin"
+    "core/built"
   ]
 }