docs(NODE-4263): document initialize bulk op function require connection

[nbbeeken]

Description

What is changing?

API documentation calling out that initializeUnorderedBulkOp and initializeOrderedBulkOp require a connected client.

What is the motivation for this change?

These APIs rely on information obtained from the hello response from the server. Restructuring the code to run batching logic after a hello has been exchanged would be a significant amount of effort. We defer to a future project to make this possible.

NODE-4263
Follow up: https://jira.mongodb.org/browse/NODE-4360

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