Update prettyplease to format macros better

[dtolnay]

Before:

assert_eq!(
    ::std::mem::size_of:: < rte_ipv4_tuple > (), 12usize, concat!("Size of: ",
    stringify!(rte_ipv4_tuple))
);

After:

assert_eq!(
    ::std::mem::size_of::<rte_ipv4_tuple>(),
    12usize,
    concat!("Size of: ", stringify!(rte_ipv4_tuple)),
);