Follow up the python 3.11 and 3.12 support from:
* commit 43844c5d82 (FindPython: Add support for Python 3.11,
2021-12-07, v3.22.2~20^2)
* commit ca2877c039 (FindPython: add support for Python 3.12,
2022-05-11, v3.23.2~15^2)
with an update for the FindBoost test.
The Gentoo case added by commit 1673923c30 (FindBoost: Add support for
Boost 1.67 with Python version suffixes, 2018-03-18, v3.11.0~3^2) left
out the `.` version component separator and instead duplicated the RPM
case. Add the missing `.` now.
Fixes: #18743