[skip ci] Update comment for alter alias (#8918)

Signed-off-by: Nyudong.cai <yudong.cai@zilliz.com>

internal/types/types.go

@@ -284,6 +284,15 @@ type RootCoord interface {
 	// otherwise, the `ErrorCode` of `Status` will be `Error`, and the `Reason` of `Status` will record the fail cause.
 	// error is always nil
 	DropAlias(ctx context.Context, req *milvuspb.DropAliasRequest) (*commonpb.Status, error)
+
+	// AlterAlias notifies RootCoord to alter alias for the collection
+	//
+	// ctx is the context to control request deadline and cancellation
+	// req contains the request params, including collection name and new alias
+	//
+	// The `ErrorCode` of `Status` is `Success` if alter alias successfully;
+	// otherwise, the `ErrorCode` of `Status` will be `Error`, and the `Reason` of `Status` will record the fail cause.
+	// error is always nil
 	AlterAlias(ctx context.Context, req *milvuspb.AlterAliasRequest) (*commonpb.Status, error)
 
 	//global timestamp allocator