Upgrade FreeBSD VM action to version 1.3.6

[rdmark]

Updated FreeBSD VM action version while downgrading to v14.3 as a workaround for a broken valgrind on v15.0

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[github-actions]

File	Coverage	Lines	Branches
All files	68%	73%	63%	✅
bstring/bstraux.c	55%	64%	46%	✅
bstring/bstrlib.c	73%	76%	69%	✅

Minimum allowed coverage is 50%

Generated by 🐒 cobertura-action against 8c99372

[rdmark]

valgrind on FreeBSD v15.0 throws this error:

==1830== Memcheck, a memory error detector
==1830== Copyright (C) 2002-2024, and GNU GPL'd, by Julian Seward et al.
==1830== Using Valgrind-3.25.1 and LibVEX; rerun with -h for copyright info
==1830== Command: /home/runner/work/bstring/bstring/build/tests/testaux
==1830== 
==1830== unhandled sysarch cmd 136
==1830== Valgrind detected that your program requires
==1830== the following unimplemented functionality:
==1830==    unhandled sysarch cmd
==1830== This may be because the functionality is hard to implement,
==1830== or because no reasonable program would behave this way,
==1830== or because nobody has yet needed it.  In any case, let us know at
==1830== www.valgrind.org and/or try to work around the problem, if you can.
==1830== 
==1830== Valgrind has to exit now.  Sorry.  Bye!
==1830== 

curiously, the exact same valgrind version on FreeBSD 14.3 works fine and executes its memory analysis