Delete type-ignore node

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## Summary

This PR removes the type ignore node from the AST because our parser doesn't support it, and just having it around is confusing.

<!-- What's the purpose of the change? What does it do, and why? -->

## Test Plan

`cargo build`

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crates/ruff_python_ast/tests/preorder.rs

@@ -5,12 +5,12 @@ use insta::assert_snapshot;
 use ruff_python_ast::node::AnyNodeRef;
 use ruff_python_ast::visitor::preorder::{
     walk_alias, walk_arg, walk_arguments, walk_comprehension, walk_except_handler, walk_expr,
-    walk_keyword, walk_match_case, walk_module, walk_pattern, walk_stmt, walk_type_ignore,
-    walk_type_param, walk_with_item, PreorderVisitor,
+    walk_keyword, walk_match_case, walk_module, walk_pattern, walk_stmt, walk_type_param,
+    walk_with_item, PreorderVisitor,
 };
 use ruff_python_ast::{
     Alias, Arg, Arguments, BoolOp, CmpOp, Comprehension, Constant, ExceptHandler, Expr, Keyword,
-    MatchCase, Mod, Operator, Pattern, Stmt, TypeIgnore, TypeParam, UnaryOp, WithItem,
+    MatchCase, Mod, Operator, Pattern, Stmt, TypeParam, UnaryOp, WithItem,
 };
 use ruff_python_parser::lexer::lex;
 use ruff_python_parser::{parse_tokens, Mode};
@@ -273,12 +273,6 @@ impl PreorderVisitor<'_> for RecordVisitor {
         self.exit_node();
     }
 
-    fn visit_type_ignore(&mut self, type_ignore: &TypeIgnore) {
-        self.enter_node(type_ignore);
-        walk_type_ignore(self, type_ignore);
-        self.exit_node();
-    }
-
     fn visit_type_param(&mut self, type_param: &TypeParam) {
         self.enter_node(type_param);
         walk_type_param(self, type_param);

crates/ruff_python_ast/tests/visitor.rs

@@ -144,11 +144,7 @@ where
     V: Visitor<'a> + ?Sized,
 {
     match module {
-        ast::Mod::Module(ast::ModModule {
-            body,
-            range: _,
-            type_ignores: _,
-        }) => {
+        ast::Mod::Module(ast::ModModule { body, range: _ }) => {
             visitor.visit_body(body);
         }
         ast::Mod::Interactive(ast::ModInteractive { body, range: _ }) => {