Revert "Fix a11y cache correctness bug"

This fix introduced a painful crash that ends up disabling accessibility
services for certain users.
This happens when a client of AccessibilityCache tries to add a node, with the same id as a node previously in the cache, but fewer children, where the removed child is not in the cache.
This is because, when children are removed, and a the node is updated, the cache tries to clear the child trees. But if the child is not in the cache, the cache clears the whole tree. Every node is recycled.
Then the original node being replaced is attempted to be recycled again, and voila crash.

The fix also didn't fix the original issue based on the discussion in
b/114133438.

The risk for this is pretty low, since nothing was built on top of this.

This reverts commit 2f69c16c.
Bug: 124676705
Test: Tested to see if above usecase still happens.

Change-Id: I8a39698c4532a1613ba47e1c6ca70201cd496212