oidc client id and secret are encoded

### Description

special character in oidc client id and secret transmitted url encoded

### Steps to reproduce

- setup oidc idp with client id and secret which contains non alphanumeric charaters
- setup synapse
- login does not work

### Homeserver

my

### Synapse Version

v1.100.0

### Installation Method

Docker (matrixdotorg/synapse)

### Database

postgresal

### Workers

Single process

### Platform

K3s single node

### Configuration

_No response_

### Relevant log output

```shell
invalid_client
```

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

_No response_