Remove sticks

For removing an item from a loot table, the entry_remove action should be used in most cases.
Using pool_remove would remove the whole pool, including all the other entries in there.

{
  "actions": [
    {
      "type": "loot-table-modifier:entry_remove"
    }
  ],
  "predicate": {
    "type": "loot-table-modifier:entry_item",
    "name": "minecraft:stick"
  }
}

Explanation

The action entry_remove removes the matched entries from their pools.

The predicate entry_item matches entries containing a stick.