[Doc]Fix 'git remote' command in contribution doc (#470)

* fix docs remote instead of remove

* Update CONTRIBUTORS.md

CONTRIBUTORS.md

@@ -21,3 +21,4 @@ Other improvement
 * [@giuseppefutia](https://github.com/giuseppefutia)
 * [@mori97](https://github.com/mori97)
 * Hao Jin
+* [@aymenwah](https://github.com/aymenwah)

docs/source/contribute.rst

@@ -43,7 +43,7 @@ Setup the upstream to the DGL official repository:
 
    git remote add upstream https://github.com/dmlc/dgl.git
 
-You could verify the remote setting by typing ``git remove -v``:
+You could verify the remote setting by typing ``git remote -v``:
 
 .. code-block:: bash