Disable media_patterns for mautrix-discord

Media didn't work before this patch, likely because this feature is broken:

> N.B. Discord now requires signed expiring download links, which means this solution no longer works. In the future, a more dynamic solution may be implemented where requests go to the bridge and the bridge and the bridge refetches the message if necessary.

Source: https://docs.mau.fi/bridges/go/discord/direct-media.html

Moreover, most users more likely don't want this behavior and would
prefer to keep a complete mirror of the media on Matrix, instead of
going through two 3rd party servers to fetch the media on demand.

The default config for the bridge
(https://github.com/mautrix/discord/blob/main/example-config.yaml)
actually does not enable it.

It seems like 4ed522e8fefff632523d68c7d2f2f9a6d86e3b1b
(https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/3133)
lied to us as to what upstream does. Poor PR review lead to this
anti-feature making it into the playbook.

roles/custom/matrix-bridge-mautrix-discord/templates/config.yaml.j2

@@ -149,7 +149,7 @@ bridge:
     # More details can be found at https://docs.mau.fi/bridges/go/discord/direct-media.html
     media_patterns:
         # Should custom mxc:// URIs be used instead of reuploading media?
-        enabled: true
+        enabled: false
         # Pattern for normal message attachments.
         attachments: {% raw %}mxc://discord-media.mau.dev/attachments|{{.ChannelID}}|{{.AttachmentID}}|{{.FileName}}{% endraw %}
         # Pattern for custom emojis.