chore: remove breaking update test fixture

.github/breaking-updates.json

@@ -1,27 +1,4 @@
 {
   "schemaVersion": 1,
-  "updates": [
-    {
-      "id": "test-breaking-update-20260715",
-      "enabled": true,
-      "introducedCommit": "",
-      "title": {
-        "zh": "测试兼容性更新",
-        "en": "Test compatibility update"
-      },
-      "summary": {
-        "zh": "这是一项用于验证自动更新保护机制的测试通知，不包含实际破坏性变更。",
-        "en": "This is a test notice for validating the automatic update protection mechanism. It does not contain an actual breaking change."
-      },
-      "changes": {
-        "zh": [
-          "本次仅用于测试通知和暂停逻辑"
-        ],
-        "en": [
-          "This test only validates the notification and pause logic"
-        ]
-      },
-      "announcementUrl": "https://github.com/MarSeventh/CloudFlare-ImgBed/releases"
-    }
-  ]
+  "updates": []
 }