[FIX] developer/rd-training: fix commands

Changed commands that were still referring to Odoo 14.0 to 15.0

closes #1879

X-original-commit: b578f57
Signed-off-by: Antoine Vandevenne (anv) <anv@odoo.com>

Author: adrienmilis

content/developer/howtos/rdtraining/02_setup.rst

@@ -148,22 +148,22 @@ Here are some useful git commands for your day-to-day work.
   .. code-block:: console
 
     $ cd $HOME/src/odoo
-    $ git checkout 14.0
+    $ git checkout saas-15.3
 
     $ cd $HOME/src/enterprise
-    $ git checkout 14.0
+    $ git checkout saas-15.3
 
 * Fetch and rebase:
 
   .. code-block:: console
 
     $ cd $HOME/src/odoo
     $ git fetch --all --prune
-    $ git rebase --autostash odoo/14.0
+    $ git rebase --autostash odoo/saas-15.3
 
     $ cd $HOME/src/enterprise
     $ git fetch --all --prune
-    $ git rebase --autostash enterprise/14.0
+    $ git rebase --autostash enterprise/saas-15.3
 
 
 Install the dependencies