FEATURE: Make Mixtral tokenizer available for embeddings (#1258)

Author: romanrizzi

app/models/embedding_definition.rb

@@ -23,6 +23,7 @@ def tokenizer_names
         DiscourseAi::Tokenizer::GeminiTokenizer,
         DiscourseAi::Tokenizer::MultilingualE5LargeTokenizer,
         DiscourseAi::Tokenizer::OpenAiTokenizer,
+        DiscourseAi::Tokenizer::MixtralTokenizer,
       ].map(&:name)
     end