Revert "strongswan: add strongswan-mod-socket"

Revert "strongswan: add strongswan-mod-socket"

The original PR for this change is #16373, where it's cleary stated it
doesn't work. This should have never been merged. It causes the
following recursive dependency:

tmp/.config-package.in:122354:error: recursive dependency detected!
tmp/.config-package.in:122354:  symbol PACKAGE_strongswan-default depends on PACKAGE_strongswan-mod-socket-default
tmp/.config-package.in:123534:  symbol PACKAGE_strongswan-mod-socket-default is selected by PACKAGE_strongswan-default

This reverts commit 603f70e96b4dc1b9e442a38cb692de519c1cd54a.

Signed-off-by: Stijn Tintel <stijn@linux-ipv6.be>