Drop an unused unpack flagged by ruff

_prepare_bool_operand() only needs the pointer depth, not the base type.
Keeps expr_pass.py at the same ruff error count as master.

Author: Douglas Mun

pythonbpf/expr/expr_pass.py

@@ -429,7 +429,7 @@ def _prepare_bool_operand(func, builder, val):
     zero-valued pointee rather than faulting -- exactly the fallback that
     `prev or 0` asks for.
     """
-    base_type, depth = get_base_type_and_depth(val.type)
+    _, depth = get_base_type_and_depth(val.type)
     if depth > 0:
         deref = deref_to_depth(func, builder, val, depth)
         if deref is not None: