FIX matinf link in ADD_NEW_DATASET.md (huggingface#1096)

ADD_NEW_DATASET.md

@@ -90,7 +90,7 @@ You can also start (or copy any part) from one of the datasets of reference list
 - summarization: [billsum](https://github.com/huggingface/datasets/blob/master/datasets/billsum/billsum.py) (original data are in json files)
 - benchmark: [glue](https://github.com/huggingface/datasets/blob/master/datasets/glue/glue.py) (original data are various formats)
 - multilingual: [xquad](https://github.com/huggingface/datasets/blob/master/datasets/xquad/xquad.py) (original data are in json)
-- multitask: [matinf](https://github.com/huggingface/datasets/blob/master/datasets/xquad/xquad.py) (original data need to be downloaded by the user because it requires authentificaition)
+- multitask: [matinf](https://github.com/huggingface/datasets/blob/master/datasets/matinf/matinf.py) (original data need to be downloaded by the user because it requires authentificaition)
 
 While you are developping the dataset script you can list test it by opening a python interpreter and running the script (the script is dynamically updated each time you modify it):