Fix typo on repositories.
@@ -27,7 +27,7 @@ This guide will help you to get Substra source code and to start a local instanc
## Get source code
-- Define a root directory for all your Substra git repositorories (for instance `~/substra`)
+- Define a root directory for all your Substra git repositories (for instance `~/substra`)
```bash
export SUBSTRA_SOURCE=~/substra
