fix: Removed invalid user from CODEOWNERS file

Signed-off-by: Christoph Wurst <christoph@winzerhof-wurst.at>

.github/CODEOWNERS

@@ -8,7 +8,7 @@
 /apps/dav/lib/CardDAV                         @ChristophWurst @miaulalala @tcitworld
 /apps/encryption/appinfo/info.xml             @come-nc @icewind1991
 /apps/federatedfilesharing/appinfo/info.xml   @icewind1991 @danxuliu
-/apps/federation/appinfo/info.xml             @vitormattos @datenangebot
+/apps/federation/appinfo/info.xml             @datenangebot
 /apps/files/appinfo/info.xml                  @skjnldsv @Pytal @ArtificialOwl @come-nc @artonge @icewind1991 @szaimen @susnux @Fenn-CS
 /apps/files_external/appinfo/info.xml         @icewind1991 @artonge
 /apps/files_sharing/appinfo/info.xml          @skjnldsv @come-nc