Drop the lint expectations clippy 1.98 no longer fulfils (#8564)

`clippy::std_instead_of_core` stopped firing at the four places that carry
an `#[expect]` for it. All four were added for the same false positive, on
items whose `core` counterpart is still unstable.

`unfulfilled_lint_expectations` is denied through `-D warnings`, so the
three clippy jobs and the WASM check fail on current stable for every pull
request, whatever it touches.

Assisted-by: Claude Code:claude-opus-5

crates/host_env/src/fileutils.rs

@@ -445,10 +445,6 @@ pub unsafe fn fclose(fp: *mut CFile) -> core::ffi::c_int {
 // _Py_fopen_obj in cpython (Python/fileutils.c:1757-1835)
 // Open a file using std::fs::File and convert to FILE*
 // Automatically handles path encoding and EINTR retries
-#[expect(
-    clippy::std_instead_of_core,
-    reason = "false positive: core::io::ErrorKind is unstable (core_io)"
-)]
 pub fn fopen(path: &std::path::Path, mode: &str) -> std::io::Result<*mut CFile> {
     use std::fs::File;
 

crates/stdlib/src/pyexpat.rs

@@ -1,8 +1,5 @@
 //! Pyexpat builtin module
 
-// false positive: core::io::Cursor is unstable (core_io), unusable on stable
-#![expect(clippy::std_instead_of_core)]
-
 // spell-checker: ignore libexpat
 
 pub(crate) use _pyexpat::module_def;

crates/stdlib/src/ssl.rs

@@ -13,9 +13,6 @@
 //!
 //! Warning: This library contains AI-generated code and comments. Do not trust any code or comment without verification. Please have a qualified expert review the code and remove this notice after review.
 
-// false positive: core::io::{Cursor, ErrorKind} are unstable (core_io), unusable on stable
-#![expect(clippy::std_instead_of_core)]
-
 // OID (Object Identifier) management module
 mod oid;
 

crates/vm/src/stdlib/_io.rs

@@ -113,10 +113,6 @@ impl std::os::fd::AsRawFd for Fildes {
 }
 
 #[pymodule]
-#[expect(
-    clippy::std_instead_of_core,
-    reason = "false positive: core::io items (Cursor, etc.) are unstable (core_io)"
-)]
 mod _io {
     use super::*;
     use crate::{