Remove deprecated Mistral AI Codestral Mamba model (#4225)

Fixes #4225

Signed-off-by: Nicolas Krier <[email protected]>
(cherry picked from commit edc1434)

Author: nicolaskrier

models/spring-ai-mistral-ai/src/main/java/org/springframework/ai/mistralai/api/MistralAiApi.java

@@ -293,8 +293,7 @@ public enum ChatModel implements ChatModelDescription {
 		SMALL("mistral-small-latest"),
 		PIXTRAL("pixtral-12b-2409"),
 		// Free Models - Research
-		OPEN_MISTRAL_NEMO("open-mistral-nemo"),
-		OPEN_CODESTRAL_MAMBA("open-codestral-mamba");
+		OPEN_MISTRAL_NEMO("open-mistral-nemo");
 		// @formatter:on
 
 		private final String value;