Dendrite cannot load conduit media

*This issue was originally created by [**@ShadowJonathan**](https://github.com/ShadowJonathan) at .*

### Background information

- **Dendrite version or git SHA**: `221ed52`
- **Monolith or Polylith?**: Monolith
- **SQLite3 or Postgres?**: Postgres
- **Running in Docker?**: No
- **`go version`**: Go 1.17

Homeserver in question is `jp.cube64128.xyz`

These same symptoms are present on `dendrite.matrix.org`

### Description

Dendrite fails without a proper error (also see https://github.com/matrix-org/dendrite/issues/1994) when loading some media from a Conduit server.

The following MXC from `conduit.rs` loads correctly on matrix.org and any other synapse server, but fails to load on dendrite;

`mxc://conduit.rs/E649aeQG37N7VGvioBB5lrlVzt8VgPud`

Synapse

`https://matrix.org/_matrix/media/r0/download/conduit.rs/E649aeQG37N7VGvioBB5lrlVzt8VgPud`
`https://matrix.jboi.nl/_matrix/media/r0/download/conduit.rs/E649aeQG37N7VGvioBB5lrlVzt8VgPud`

Dendrite

`https://jp.cube64128.xyz/_matrix/media/r0/download/conduit.rs/E649aeQG37N7VGvioBB5lrlVzt8VgPud`
`https://dendrite.matrix.org/_matrix/media/r0/download/conduit.rs/E649aeQG37N7VGvioBB5lrlVzt8VgPud`

Conduit

`https://conduit.koesters.xyz/_matrix/media/r0/download/conduit.rs/E649aeQG37N7VGvioBB5lrlVzt8VgPud`
`https://beta.automatia.nl/_matrix/media/r0/download/conduit.rs/E649aeQG37N7VGvioBB5lrlVzt8VgPud`

No logs, but seeing as how this occurs on `dendrite.matrix.org`, this should be easy to trace.

If there are any details on what conduit could be doing wrong here, please close this issue with it and ping @timokoesters with the details