renovate: Disable lockfile maintenance

Requested in rust-lang/team#2519 (comment)

Author: Turbo87

.github/renovate.json5

@@ -3,12 +3,5 @@
   // Let Renovatebot keep an opened issue that tracks our dependencies
   "dependencyDashboard": true,
   // Disable "normal" package updates
-  "enabledManagers": [],
-  // Update lockfiles once per week
-  "lockFileMaintenance": {
-    "enabled": true,
-    "schedule": [
-      "before 5am on Tuesday"
-    ]
-  }
+  "enabledManagers": []
 }