Clarify what services do *not* count against Simultaneous open connections limit

### Existing documentation URL(s)

https://developers.cloudflare.com/workers/platform/limits/#simultaneous-open-connections

### What changes are you suggesting?

This list currently includes `fetch()`, Workers KV, Cache, R2, Queues, `connect()` and a note at the bottom about limits being shared with Service Bindings.

There are a few actions that feel like they may contribute to the limits, that aren't documented:
- Performing a query on a D1 database
- Whether Durable Objects share resources from the top-level request
- A Service Bindings call (pretty sure this one doesn't count)
- A Durable Objects call (if it's in a different region, is it over a socket?)

If they do contribute, I'd like to add them. If they don't, I'd like to explicitly document them as not contributing to the limit.

### Additional information

Happy to make the PR for this, but would like clarification first.