fixed assembly issue during build

Author: hiroki-o

Editor/com.unity.animations.springbone.editor.asmdef

@@ -3,12 +3,15 @@
     "references": [
         "com.unity.animations.springbone"
     ],
-    "optionalUnityReferences": [],
-    "includePlatforms": [],
+    "includePlatforms": [
+        "Editor"
+    ],
     "excludePlatforms": [],
     "allowUnsafeCode": false,
     "overrideReferences": false,
     "precompiledReferences": [],
     "autoReferenced": true,
-    "defineConstraints": []
+    "defineConstraints": [],
+    "versionDefines": [],
+    "noEngineReferences": false
 }