Fix: Nested list indendation in editor for classic themes

[karthikeya-io]

What?

Closes #69503
Related https://wordpress.org/support/topic/list-block-no-visual-nested-indent/

Why?

Fix nested list indentation in editor for classic themes.

This fixes the nested list indentation in the editor for following themes.

• 2014, 15, 16, 17

How?

Prevents applying margin-left:auto and margin-right: auto to nested lists

Testing Instructions

1. Activate Twenty Fifteen.
2. Create a new post and add a list block.
3. Add multiple list item and indent them with different depths.
4. Confirm that the nested list items are visually indented as expected.

Testing Instructions for Keyboard

Same

Screenshots or screencast

Before	After

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[sabernhardt]

#60802 raised the specificity to the previous level of 0-2-0, but I do not think it should increase any more.

Suggested change

	.editor-styles-wrapper :where(:not(.is-layout-flex, .is-layout-grid)) > .wp-block:not(.wp-block-list .wp-block-list) {
	.editor-styles-wrapper :where(:not(.is-layout-flex, .is-layout-grid)) > .wp-block:where(:not(.wp-block-list .wp-block-list)) {

[karthikeya-io]

Thanks for the feedback, Have updated the specificity.