Added dm-tree library to known list (#2789)

## Changes
Whitelists dm-tree

### Linked issues
Partly resolve #1931

Author: pritishpai

src/databricks/labs/ucx/source_code/known.json

@@ -3731,6 +3731,11 @@
     "distro": [],
     "distro.distro": []
   },
+  "dm-tree": {
+    "tree": [],
+    "tree.sequence": [],
+    "tree.tree_benchmark": []
+  },
   "docker": {
     "docker": []
   },