Wrong formatting when both alignment and '0' for leading zeroes is given

[stefanhaller]

According to https://en.cppreference.com/w/cpp/utility/format/formatter: "If the 0 character and an align option both appear, the 0 character is ignored."

fmt::print("{:<06}\n", -42); // expected: "-42   ", actual: "-42000"
fmt::print("{:>06}\n", -42); // expected: "   -42", actual: "000-42"