net-p2p/bitcoin*: remove db48 dependency
In r465909 [1], 2 years ago, we added the option to link
net-p2p/bitcoin* against db 5 or 6, still allowing to link against db
4.8 which is long time EOL and has been deprecated and marked for
deletion in 2014 [2].
Now remove the option to link net-p2p/bitcoin* against db48, so the
former does not depend on the latter anymore and db48 can be eventually
removed from the ports tree.
[1]
https://svnweb.freebsd.org/ports?view=revision&revision=465909
https://github.com/freebsd/freebsd-ports/commit/68892c74876772806eaca3a9ecc1308e9459acea
PR: 245220
Submitted by: vd
Approved by: kbowling (maintainer timeout)