Added lz4 to known list (#2994)

## Changes
Added `lz4` to known list 

### Linked issues
Partly resolve #1931

Author: pritishpai

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

@@ -10394,6 +10394,12 @@
   "lxml": {
     "lxml": []
   },
+  "lz4": {
+    "lz4": [],
+    "lz4.block": [],
+    "lz4.frame": [],
+    "lz4.version": []
+  },
   "mako": {
     "mako": []
   },
@@ -32721,4 +32727,4 @@
     "zipp.compat.py310": [],
     "zipp.glob": []
   }
-}
+}