Wrong MSRV for windows

[Emilgardis]

libc on target x86_64-pc-windows-msvc has a msrv of 1.47 due too #2409

This was found in cross-rs/cross#549

failure on 1.42.0-x86_64-pc-windows-msvc is

error[E0277]: arrays only have std trait implementations for lengths 0..=32
   --> C:\Users\VssAdministrator\.cargo\registry\src\github.com-1ecc6299db9ec823\libc-0.2.103\src\windows\msvc\x86_64.rs:66:9
    |
42  | / s! {
43  | |     #[repr(align(16))]
44  | |     pub struct M128A {
45  | |         pub Low: ::c_ulonglong,
...   |
66  | |         _Reserved4: [::c_uchar; 96],
    | |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `core::array::LengthAtMost32` is not implemented for `[u8; 96]`
...   |
139 | |     }
140 | | }
    | |_- in this macro invocation
    |
    = note: required because of the requirements on the impl of `core::hash::Hash` for `[u8; 96]`

[Emilgardis]

@rustbot label: +O-windows