Fix a typo

There is a typo in the text: repositories -> repository, fix it.

Author: algonell

C-git-commands.asc

@@ -380,7 +380,7 @@ We use `git archive` to create a tarball of a project for sharing in <<ch05-dist
 
 ==== git submodule
 
-The `git submodule` command is used to manage external repositories within a normal repositories.
+The `git submodule` command is used to manage external repositories within a normal repository.
 This could be for libraries or other types of shared resources.
 The `submodule` command has several sub-commands (`add`, `update`, `sync`, etc) for managing these resources.