CONTRIBUTING.md: fix module use cmd

CONTRIBUTING.md

@@ -8,7 +8,7 @@ To install your forked version of the LBMC modules repository on the PSMN run fo
 
 ```
 git clone git@gitlab.biologie.ens-lyon.fr:<your_login>/modules.git ~/privatemodules_dev
-module use ~/privatemodules_dev
+module use ~/privatemodules_dev/modulefiles/
 ```
 
 If you don’t have a `.ssh/config` file and if you like typing your password, you can instead use the following clone command, after defining your [Gitlab password](https://gitlab.biologie.ens-lyon.fr/profile/password/edit).