fix: Fix formatting of messages with newlines

Newlines were previously not formatted correctly in HTML/markdown messages.
Formatting is of newlines is implemented in the matrix-dart-sdk, but
was explicitly disabled when creating the matrix Client object.
This fixes formatting by removing the parameter from the client config,
causing the client to follow the expected, default behavior.
This only affects outgoing new messages, both old wrongly formatted
messages and new messages are rendered correctly in FluffyChat.
New messages are now also correctly formatted in other clients.

lib/utils/client_manager.dart

@@ -138,7 +138,6 @@ abstract class ClientManager {
             (share) => share.name == shareKeysWith,
           ) ??
           ShareKeysWith.all,
-      convertLinebreaksInFormatting: false,
       onSoftLogout: enableSoftLogout
           ? (client) => client.refreshAccessToken()
           : null,