Fix indentation drift for indented code blocks in list items (#19990)

Co-authored-by: fisker <lionkay@gmail.com>

tests/format/markdown/list/tab-width/__snapshots__/format.test.js.snap

@@ -0,0 +1,47 @@
+// Jest Snapshot v1, https://jestjs.io/docs/snapshot-testing
+
+exports[`indented-code-block.md - {"tabWidth":4} format 1`] = `
+====================================options=====================================
+parsers: ["markdown", "mdx"]
+tabWidth: 4
+                                                      printWidth: 80 (default) |
+=====================================input======================================
+- [x] task item
+
+      indented code
+
+- unordered item
+
+      indented code
+
+- outer item
+
+  - nested item
+
+        indented code
+
+- item with extra code indentation
+
+          indented code
+
+=====================================output=====================================
+- [x] task item
+
+      indented code
+
+- unordered item
+
+      indented code
+
+- outer item
+
+    - nested item
+
+          indented code
+
+- item with extra code indentation
+
+          indented code
+
+================================================================================
+`;

tests/format/markdown/list/tab-width/format.test.js

@@ -0,0 +1 @@
+runFormatTest(import.meta, ["markdown", "mdx"], { tabWidth: 4 });

tests/format/markdown/list/tab-width/indented-code-block.md

@@ -0,0 +1,17 @@
+- [x] task item
+
+      indented code
+
+- unordered item
+
+      indented code
+
+- outer item
+
+  - nested item
+
+        indented code
+
+- item with extra code indentation
+
+          indented code