Incorrect expected type for second arg of deep_replace

[kit1980]

Here is a full repro:

import libcst as cst

def f(node: cst.Call) -> cst.Call:
    arg = node.args[0]
    new_arg = arg.with_changes(value=cst.Integer(value="2"))
    return node.deep_replace(arg, new_arg)

node = cst.ensure_type(cst.parse_expression("func(1)"), cst.Call)
print(f(node))

So we're replacing an Arg with an Arg in a Call node, but type checker complains:
error: Argument 2 to "deep_replace" of "CSTNode" has incompatible type "Arg"; expected "Call" [arg-type]