boost: Fix rootfile entries that referred to python3.8 instead of 3.10

boost: Fix rootfile entries that referred to python3.8 instead of 3.10

- In Jan 2022 I updated python from 3.8 to 3.10 but I missed that boost had rootfile
   entries with python38 in it.
- Running a build just now for another package it got flagged up that the rootfile for
   boost had been changed and the logfile now had the entries with python310 instead of
   python38
- Not clear why it only flagged this up now but this patch is to correct that error
- Running find-dependencies on both the pyton38 and python310 versions of the libraries
  flagged nothing as being linked to either, so probably lucky with this being missed
  first time around.
- Boost will need to be shipped with a Core Update

Signed-off-by: Adolf Belka <adolf.belka@ipfire.org>
Reviewed-by: Peter Müller <peter.mueller@ipfire.org>