Let’s Encrypt certificates for TURNS are rejected

I tried dev 0.23 build from https://buildkite.com/matrix-dot-org/riotx-android/builds/2964

It has the same TURNS error reported previously, [here](https://github.com/vector-im/riot-android/issues/3299) and [here](https://github.com/matrix-org/synapse/issues/6201). The coturn is checked it with is 4.5.1.2.

The coturn config looks like so,
```

listening-port=3478
tls-listening-port=5349
alt-listening-port=3479
alt-tls-listening-port=5350
listening-ip=192.168.1.10
external-ip=xx.xx.xx.xx
min-port=49152
max-port=65535
verbose
fingerprint
use-auth-secret
static-auth-secret=xx
realm=turn.mydomain.com
userdb=/var/lib/turnserver/turndb
stale-nonce=600
cert=/etc/letsencrypt/live/mydomain.com/fullchain.pem
pkey=/etc/letsencrypt/live/mydomain.com/privkey.pem
cipher-list="ECDH+AESGCM:DH+AESGCM:ECDH+AES256:DH+AES256:ECDH+AES128:DH+AES:ECDH+3DES:DH+3DES:RSA+AES:RSA+3DES:!ADH:!AECDH:!MD5"
no-multicast-peers
mobility
cli-password=xx
no-tlsv1
no-tlsv1_1
```