Stabilize allowance of os.environ modifications between imports (#12047)

## Summary

See: #10066.

crates/ruff_linter/src/checkers/ast/mod.rs

@@ -462,8 +462,7 @@ impl<'a> Visitor<'a> for Checker<'a> {
                     || helpers::in_nested_block(self.semantic.current_statements())
                     || imports::is_matplotlib_activation(stmt, self.semantic())
                     || imports::is_sys_path_modification(stmt, self.semantic())
-                    || (self.settings.preview.is_enabled()
-                        && imports::is_os_environ_modification(stmt, self.semantic())))
+                    || imports::is_os_environ_modification(stmt, self.semantic()))
                 {
                     self.semantic.flags |= SemanticModelFlags::IMPORT_BOUNDARY;
                 }

crates/ruff_linter/src/rules/pycodestyle/mod.rs

@@ -69,7 +69,6 @@ mod tests {
     }
 
     #[test_case(Rule::IsLiteral, Path::new("constant_literals.py"))]
-    #[test_case(Rule::ModuleImportNotAtTopOfFile, Path::new("E402_2.py"))]
     #[test_case(Rule::RedundantBackslash, Path::new("E502.py"))]
     #[test_case(Rule::TooManyNewlinesAtEndOfFile, Path::new("W391_0.py"))]
     #[test_case(Rule::TooManyNewlinesAtEndOfFile, Path::new("W391_1.py"))]

crates/ruff_linter/src/rules/pycodestyle/rules/module_import_not_at_top_of_file.rs

@@ -13,12 +13,9 @@ use crate::checkers::ast::Checker;
 /// According to [PEP 8], "imports are always put at the top of the file, just after any
 /// module comments and docstrings, and before module globals and constants."
 ///
-/// This rule makes an exception for `sys.path` modifications,  allowing for
-/// `sys.path.insert`, `sys.path.append`, and similar modifications between import
-/// statements.
-///
-/// In [preview], this rule also allows `os.environ` modifications between import
-/// statements.
+/// This rule makes an exception for both `sys.path` modifications (allowing for
+/// `sys.path.insert`, `sys.path.append`, etc.) and `os.environ` modifications
+/// between imports.
 ///
 /// ## Example
 /// ```python
@@ -40,7 +37,6 @@ use crate::checkers::ast::Checker;
 /// ```
 ///
 /// [PEP 8]: https://peps.python.org/pep-0008/#imports
-/// [preview]: https://docs.astral.sh/ruff/preview/
 #[violation]
 pub struct ModuleImportNotAtTopOfFile {
     source_type: PySourceType,

crates/ruff_linter/src/rules/pycodestyle/snapshots/ruff_linter__rules__pycodestyle__tests__E402_E402_2.py.snap

@@ -1,12 +1,4 @@
 ---
 source: crates/ruff_linter/src/rules/pycodestyle/mod.rs
 ---
-E402_2.py:7:1: E402 Module level import not at top of file
-  |
-5 | del os.environ["WORLD_SIZE"]
-6 | 
-7 | import torch
-  | ^^^^^^^^^^^^ E402
-  |
-