Remove antimixedutf8 changes from release notes

[skip ci]

doc/RELEASE-NOTES.md

@@ -64,10 +64,6 @@ in progress and may not be a stable version.
   messages. Generally it is very useful to see if a spamfilter hit is
   correct or not, so the default is 'always', but it also has privacy
   implications so there is now this option to disable it.
-* The module [antimixedutf8](https://www.unrealircd.org/docs/Set_block#set::antimixedutf8)
-  now recognizes more code block transitions and should do a better job at
-  catching mixed UTF8 spam. It may also have more false positives.
-  This module is (still) not loaded by default.
 * You can restrict includes to only contain certain blocks, the style is:
   ```
   include "some-file-or-url" { restrict-config { name-of-block; name-of-block2; } }