Update how_to_register_samples.md

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 # How to register new samples?
 
-For the exercise, you can use this dataset as a example file.
-<a href="../images/XPLAIN_data_TP.xlsx" download>Click to Download</a>
+For the exercise, you can use <a href="../images/XPLAIN_data_TP.xlsx" download>this dataset as an example file.</a>
 
 ### 1- Register Biosample