[IMP] conf.py, *: interpolate the version and releases in the content

This commit replaces hard-coded occurrences of the version and of the
last, current and next releases' version with placeholders interpolated
at build time to avoid manually updating these after each freeze.

task-2917614

closes odoo/documentation#3166

X-original-commit: 12e1085199
Signed-off-by: Antoine Vandevenne (anv) <anv@odoo.com>

content/developer/howtos/rdtraining/05_securityintro.rst

@@ -17,9 +17,9 @@ Data Files (CSV)
 
 Odoo is a highly data driven system. Although behavior is customized using Python code, part of a
 module's value is in the data it sets up when loaded. One way to load data is through a CSV
-file. One example is the
-`list of country states <https://github.com/odoo/odoo/blob/16.0/odoo/addons/base/data/res.country.state.csv>`__
-which is loaded at installation of the ``base`` module.
+file. One example is the `list of country states
+<{GITHUB_PATH}/odoo/addons/base/data/res.country.state.csv>`_ which is loaded at installation of the
+`base` module.
 
 .. code-block:: text