fix: no deref index-expr for extract_function

Example
---
```rust
fn foo() {
    let mut arr = [1i32];
    $0arr[0] = 3;$0
    let _ = arr;
}
```

**Before this PR**

```rust
fn foo() {
    let mut arr = [1i32];
    fun_name(&mut arr);
    let _ = arr;
}

fn $0fun_name(arr: &mut [i32; 1]) {
    *arr[0] = 3;
}
```

**After this PR**

```rust
fn foo() {
    let mut arr = [1i32];
    fun_name(&mut arr);
    let _ = arr;
}

fn $0fun_name(arr: &mut [i32; 1]) {
    arr[0] = 3;
}
```

Author: A4-Tacks

crates/ide-assists/src/handlers/extract_function.rs

@@ -2088,7 +2088,11 @@ fn fix_param_usages(
     for (param, usages) in usages_for_param {
         for usage in usages {
             match usage.syntax().ancestors().skip(1).find_map(ast::Expr::cast) {
-                Some(ast::Expr::MethodCallExpr(_) | ast::Expr::FieldExpr(_)) => {
+                Some(
+                    ast::Expr::MethodCallExpr(_)
+                    | ast::Expr::FieldExpr(_)
+                    | ast::Expr::IndexExpr(_),
+                ) => {
                     // do nothing
                 }
                 Some(ast::Expr::RefExpr(node))
@@ -3211,6 +3215,32 @@ fn $0fun_name(n: &mut i32) {
         );
     }
 
+    #[test]
+    fn mut_index_from_outer_scope() {
+        check_assist(
+            extract_function,
+            r#"
+//- minicore: index
+fn foo() {
+    let mut arr = [1i32];
+    $0arr[0] = 3;$0
+    let _ = arr;
+}
+"#,
+            r#"
+fn foo() {
+    let mut arr = [1i32];
+    fun_name(&mut arr);
+    let _ = arr;
+}
+
+fn $0fun_name(arr: &mut [i32; 1]) {
+    arr[0] = 3;
+}
+"#,
+        );
+    }
+
     #[test]
     fn mut_field_from_outer_scope() {
         check_assist(