Remove 'non-obvious' allowance for E721 (#12300)

## Summary

I don't fully understand the purpose of this. In #7905, it was just
copied over from the previous non-preview implementation. But it means
that (e.g.) we don't treat `type(self.foo)` as a type -- which is wrong.

Closes #12290.

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

@@ -16,10 +16,7 @@ use crate::checkers::ast::Checker;
 /// Unlike a direct type comparison, `isinstance` will also check if an object
 /// is an instance of a class or a subclass thereof.
 ///
-/// Under [preview mode](https://docs.astral.sh/ruff/preview), this rule also
-/// allows for direct type comparisons using `is` and `is not`, to check for
-/// exact type equality (while still forbidding comparisons using `==` and
-/// `!=`).
+/// If you want to check for an exact type match, use `is` or `is not`.
 ///
 /// ## Example
 /// ```python
@@ -74,18 +71,7 @@ pub(crate) fn type_comparison(checker: &mut Checker, compare: &ast::ExprCompare)
 /// Returns `true` if the [`Expr`] is known to evaluate to a type (e.g., `int`, or `type(1)`).
 fn is_type(expr: &Expr, semantic: &SemanticModel) -> bool {
     match expr {
-        Expr::Call(ast::ExprCall {
-            func, arguments, ..
-        }) => {
-            // Allow comparison for types which are not obvious.
-            if !arguments
-                .args
-                .first()
-                .is_some_and(|arg| !arg.is_name_expr() && !arg.is_none_literal_expr())
-            {
-                return false;
-            }
-
+        Expr::Call(ast::ExprCall { func, .. }) => {
             // Ex) `type(obj) == type(1)`
             semantic.match_builtin_expr(func, "type")
         }

crates/ruff_linter/src/rules/pycodestyle/snapshots/ruff_linter__rules__pycodestyle__tests__E721_E721.py.snap

@@ -40,6 +40,16 @@ E721.py:21:8: E721 Use `is` and `is not` for type comparisons, or `isinstance()`
 23 | assert type(res) == type([])
    |
 
+E721.py:21:36: E721 Use `is` and `is not` for type comparisons, or `isinstance()` for isinstance checks
+   |
+19 |     pass
+20 | #: E721
+21 | assert type(res) == type(False) or type(res) == type(None)
+   |                                    ^^^^^^^^^^^^^^^^^^^^^^^ E721
+22 | #: E721
+23 | assert type(res) == type([])
+   |
+
 E721.py:23:8: E721 Use `is` and `is not` for type comparisons, or `isinstance()` for isinstance checks
    |
 21 | assert type(res) == type(False) or type(res) == type(None)