fix: disable uadd operator (#3174)

it should have been disabled, but there was some code which was never
removed which bypassed the check.

Author: charles-cooper

tests/parser/exceptions/test_syntax_exception.py

@@ -74,6 +74,11 @@ def foo():
     """
 a: internal(uint256)
     """,
+    """
+@external
+def foo():
+    x: uint256 = +1  # test UAdd ast blocked
+    """,
 ]
 
 

vyper/ast/annotation.py

@@ -230,11 +230,6 @@ def visit_UnaryOp(self, node):
         """
         self.generic_visit(node)
 
-        # TODO once grammar is updated, remove this
-        # UAdd has no effect on the value of it's operand, so it is discarded
-        if isinstance(node.op, python_ast.UAdd):
-            return node.operand
-
         is_sub = isinstance(node.op, python_ast.USub)
         is_num = (
             hasattr(node.operand, "n")