firebase-tools: firebase deploy firebase:indexes fails when any index was already created

[REQUIRED] Environment info

firebase-tools: 7.0.2

Platform: Ubuntu

[REQUIRED] Test case

v1: indexes.json

{
  "indexes": [
    {
      "collectionGroup": "authors",
      "queryScope": "COLLECTION",
      "fields": [
        {
          "fieldPath": "name",
          "order": "ASCENDING"
        },
        {
          "fieldPath": "born",
          "order": "ASCENDING"
        }
      ]
    }
  ]
}

v2: indexes.json: added new index

{
  "indexes": [
    {
      "collectionGroup": "authors",
      "queryScope": "COLLECTION",
      "fields": [
        {
          "fieldPath": "name",
          "order": "ASCENDING"
        },
        {
          "fieldPath": "born",
          "order": "ASCENDING"
        }
      ]
    },
    {
      "collectionGroup": "authors",
      "queryScope": "COLLECTION",
      "fields": [
        {
          "fieldPath": "name",
          "order": "ASCENDING"
        },
        {
          "fieldPath": "born",
          "order": "DESCENDING"
        }
      ]
    }
  ]
}

[REQUIRED] Steps to reproduce

1. run firebase deploy --only firestore:indexes with first version of indexes.json
2. update file with additional index and re-run

[REQUIRED] Expected behavior

Both commands are successful and target firestore database contains both indices

[REQUIRED] Actual behavior

First run succeeds, but latter fails with error: Error: HTTP Error: 409, index already exists. Only first index is present.

Workaround

1. Delete all indexes before deploy
2. Place in indexes.json only indexes not present in database.

It would seems this has been caused by: #1120