Clean up LLD_UNSAFE from openal-soft ports
After FreeBSD 12.0 EOL we no longer have to worry about LLD 6 and
can drop LLD_UNSAFE from openal-soft ports. LLD can link them fine
now but some ports needs a little help on i386 (-Wl,-znotext).
PR: 226980
Reviewed by: jbeich (earlier version)
Differential Revision: https://reviews.freebsd.org/D23030