Redactions does not work with btree keys

[danielgatis]

Description

redactions does not works for btree keys.

Reproduction steps

In test:

insta::assert_yaml_snapshot!(&book, {
    ".**.timestamp" => "[timestamp]"
});

result:

market: USD/BTC
bids:
  side: 1
  map: {}
  tree: {}
asks:
  side: 0
  map:
    1:
      id: 1
      trader_id: 1
      price: 500
      qty: 5
      timestamp: "[timestamp]"
      side: 0
  tree:
    ? price: 500
      timestamp: 1629899989141
      side: 0
    : id: 1
      trader_id: 1
      price: 500
      qty: 5
      timestamp: "[timestamp]"
      side: 0
seq: 1

Additional helpful information:

• Version of insta: 1.7.2
• Version of rustc: v1.56.0-nightly
• Operating system and version: macOS 11.5.1

What did you expect

The timestamp in the btree key should be replaced.