`startAfter` doesn't work when given a document ref while an `orderBy` is also present

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### A screenshot that you have tested with "Try this API".


### Link to the code that reproduces this issue. A link to a **public** Github Repository or gist with a minimal reproduction.

https://github.com/ashtonmoomoo/firestore-bug

### A step-by-step description of how to reproduce the issue, based on the linked reproduction.

1. Clone the repo linked in this issue
2. Install dependencies with `npm i`
3. Update the configuration at the top of `repro.ts`
4. Run `npm run repro`

### A clear and concise description of what the bug is, and what you expected to happen.

I expect supplying a _document reference_ to `startAfter` while a `orderBy` is present to work in the same way as it does when supplying a _document snapshot_ to `startAfter` in the same scenario.

Using the reproduction script in the supplied repo, I expect the `size` of each resulting query snapshot to be 1. The last example query in the script has a size of 0.

### A clear and concise description WHY you expect this behavior, i.e., was it a recent change, there is documentation that points to this behavior, etc. **

As illustrated by the example queries in the script, using `startAfter` should behave the same whether it is given a snapshot or a ref, regardless of what other query clauses are present.