Remove SSE ABI from i586-pc-windows-msvc

As an i586 target, it should not have SSE. This caused the following
warning to be emitted:

```
warning: target feature `sse2` must be enabled to ensure that the ABI of the current target can be implemented correctly
  |
  = note: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
  = note: for more information, see issue rust-lang#116344 <rust-lang#116344>

warning: 1 warning emitted
```

compiler/rustc_target/src/spec/targets/i586_pc_windows_msvc.rs

@@ -2,6 +2,7 @@ use crate::spec::Target;
 
 pub(crate) fn target() -> Target {
     let mut base = super::i686_pc_windows_msvc::target();
+    base.rustc_abi = None; // overwrite the SSE2 ABI set by the base target
     base.cpu = "pentium".into();
     base.llvm_target = "i586-pc-windows-msvc".into();
     base