update an import for latest vyper commit

boa/contracts/vyper/ast_utils.py

@@ -4,7 +4,7 @@
 from typing import Any, Optional
 
 import vyper.ast as vy_ast
-from vyper.codegen.core import getpos
+from vyper.ir.compile_ir import getpos
 
 
 def get_block(source_code: str, lineno: int, end_lineno: int) -> str:
@@ -45,6 +45,8 @@ def reason_at(
 
 
 # build a reverse map from the format we have in pc_pos_map to AST nodes
+# (TODO: we might not need this anymore since vyper exports map from pc
+# to ast node directly as of 0.4.0)
 def ast_map_of(ast_node):
     ast_map = {}
     nodes = [ast_node] + ast_node.get_descendants(reverse=True)