Retry CUDA 12 migration of hoomd-dlext

This PR was closed out instead of re-run. So `hoomd-dlext` wasn't
actually migrated successfully. This requeues the `hoomd-dlext` CUDA 12
migration to generate a new migration PR.

status/migration_json/cuda120.json

@@ -219,13 +219,6 @@
       "pr_url": "https://github.com/conda-forge/hoomd-feedstock",
       "pre_pr_migrator_status": ""
     },
-    "hoomd-dlext": {
-      "immediate_children": [],
-      "num_descendants": 0,
-      "pr_status": "",
-      "pr_url": "https://github.com/conda-forge/hoomd-dlext-feedstock",
-      "pre_pr_migrator_status": ""
-    },
     "implicit": {
       "immediate_children": [],
       "num_descendants": 0,
@@ -807,4 +800,4 @@
     "pennylane-lightning-gpu"
   ],
   "not-solvable": []
-}
+}