PrintBadFuncRefs prints the "bad" function references (the function references that match those provided in sigs).
Returns an error if the check fails or if any bad references are found.
FuncRef is a reference to a specific function. Matches the string representation of *types.Func, which is of the
form "func (*net/http.Client).Do(req *net/http.Request) (*net/http.Response, error)".