Add limits for Alterations

Add limits for Alterations. This is same as Custom Question Answering.
#90241

Author: nkgami

articles/cognitive-services/QnAMaker/limits.md

@@ -123,6 +123,9 @@ These represent the limits when Prebuilt API is used to *Generate response* or c
 > [!IMPORTANT]
 > Support for unstructured file/content and is available only in question answering.
 
+## Alterations limits
+[Alterations](https://docs.microsoft.com/ja-JP/rest/api/cognitiveservices/qnamaker/alterations/replace) do not allow these special characters: ',', '?', ':', ';', '\"', '\'', '(', ')', '{', '}', '[', ']', '-', '+', '.', '/', '!', '*', '-', '_', '@', '#'
+
 ## Next steps
 
 Learn when and how to change [service pricing tiers](How-To/set-up-qnamaker-service-azure.md#upgrade-qna-maker-sku).