[documentDb\: Inaccuracy continuousModeProperties while using type 'Continuous' in backupPolicy

### Resource Type

Microsoft.DocumentDB/databaseAccounts

### Api Version

2021-01-15

### Issue Type

Inaccurate property type(s)

### Other Notes


### Bicep Repro

```bicep
param documentDbName string
param databaseName string
param locations array
param enableAutomaticFailover bool

resource documentDb 'Microsoft.DocumentDB/databaseAccounts@2021-01-15' = {
name: documentDbName
location: resourceGroup().location
kind: 'GlobalDocumentDB'
properties: {
databaseAccountOfferType: 'Standard'
consistencyPolicy: {
defaultConsistencyLevel: 'Session'
maxIntervalInSeconds: 5
maxStalenessPrefix: 100
}
enableAutomaticFailover: enableAutomaticFailover
enableMultipleWriteLocations: false
locations: [for (location, i) in locations: {
locationName: location
failoverPriority: i
}]
backupPolicy: {
type: 'Continuous'
continuousModeProperties: {
tier: 'Continuous7Days'
}
}
}
}

resource documentDbSql 'Microsoft.DocumentDB/databaseAccounts/sqlDatabases@2021-01-15' = {
name: databaseName
parent: documentDb
properties: {
resource: {
id: databaseName
}
}
}

```

### Confirm

- [X] I have read the troubleshooting guide and looked for duplicates.

No file or test is named; start by locating the Microsoft.DocumentDB/databaseAccounts@2021-01-15 resource definition and its backupPolicy schema. Compare continuousModeProperties with the supplied Bicep repro, then verify that the Continuous backup policy and Continuous7Days tier are accepted without an inaccurate type diagnostic.

Written by the indexing model from the issue text.