xmpp-parsers: Remove util::text_node_codecs

This codec system was useful for the previous parser style, but we have
converted them all to xso now!

parsers/src/util/mod.rs

@@ -4,9 +4,6 @@
 // License, v. 2.0. If a copy of the MPL was not distributed with this
 // file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
-/// Various helpers.
-pub(crate) mod text_node_codecs;
-
 /// Helper macros to parse and serialise more easily.
 #[macro_use]
 mod macros;