Apply suggestions from code review

Co-authored-by: Deborah Ferreira <dferreir@mathworks.com>

Author: MiriamScharnke

+llms/+utils/errorMessageCatalog.m

@@ -48,7 +48,7 @@
 catalog("llms:keyMustBeSpecified") = "Unable to find API key. Either set environment variable {1} or specify name-value argument ""APIKey"".";
 catalog("llms:mustHaveMessages") = "Message history must not be empty.";
 catalog("llms:mustSetFunctionsForCall") = "When no functions are defined, ToolChoice must not be specified.";
-catalog("llms:mustBeMessagesOrTxt") = "Message must be nonempty string, character array, or messageHistory object.";
+catalog("llms:mustBeMessagesOrTxt") = "Message must be nonempty string, character array, cell array of character vectors, or messageHistory object.";
 catalog("llms:invalidOptionAndValueForModel") = "'{1}' with value '{2}' is not supported for model ""{3}"".";
 catalog("llms:invalidOptionForModel") = "Invalid argument name {1} for model ""{2}"".";
 catalog("llms:invalidContentTypeForModel") = "{1} is not supported for model ""{2}"".";