Update partitionKey in Bicep resource definition

Modified the `partitionKey` property in the Bicep file, changing the path from `'/myPartitionKey'` to `'/entity'`. This change reflects an updated partitioning strategy for the database container.

Author: richard-einfinity

samples/datasync-server-cosmosdb-singlecontainer/infra/resources.bicep

@@ -59,7 +59,7 @@ resource container 'Microsoft.DocumentDB/databaseAccounts/sqlDatabases/container
       id: containerName
       partitionKey: {
         paths: [
-          '/myPartitionKey'
+          '/entity'
         ]
         kind: 'Hash'
       }