Disable clippy::std_instead_of_core lint

rust-lang/rust-clippy#12438

```
error: used import from `std` instead of `core`
   --> src/lib.rs:134:5
    |
134 | use std::{
    |     ^^^ help: consider importing the item from `core`: `core`
    |
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#std_instead_of_core
    = note: `-D clippy::std-instead-of-core` implied by `-D warnings`
    = help: to override `-D warnings` add `#[allow(clippy::std_instead_of_core)]`
```

src/lib.rs

@@ -121,7 +121,7 @@ for multiple crate names and versions. For general purposes,
     clippy::impl_trait_in_params,
     // clippy::missing_inline_in_public_items,
     // clippy::std_instead_of_alloc,
-    clippy::std_instead_of_core,
+    // clippy::std_instead_of_core,
 )]
 #![allow(clippy::must_use_candidate)]