Documentation: Missing info on "earliest version [that] can be rolled back to"

### Description

I need to upgrade an installation of Synapse. Checking the docs, I read the section "Rolling back to older versions" at https://github.com/element-hq/synapse/blob/develop/docs/upgrade.md#rolling-back-to-older-versions

In that section, it says:
> The following table gives the version ranges and the earliest version they can be rolled back to.

But there is no table following.

### Steps to reproduce

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### Homeserver

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### Synapse Version

.

### Installation Method

Docker (matrixdotorg/synapse)

### Database

.

### Workers

Single process

### Platform

.

### Configuration

_No response_

### Relevant log output

```shell
.
```

### Anything else that would be useful to know?

_No response_

Open docs/upgrade.md and read the “Rolling back to older versions” section referenced in the issue. Determine which version ranges and earliest rollback versions the missing table should cover; the work is complete when that section includes the promised table and accurately supports the documented upgrade guidance.

Written by the indexing model from the issue text.