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
closesodoo/documentation#3170
X-original-commit: fa2d0f6363
Signed-off-by: Antoine Vandevenne (anv) <anv@odoo.com>