devel/git: Add missing (send-email) dependency

The send-email command uses (require's) IO:Socket:SSL directly, and the
devel/git port previously depended on mail/p5-Net-SMTP-SSL, which depended on
and brought in the security/p5-IO-Socket-SSL port to satisfy it.

ports r431794 [1] removed the dependency on p5-Net-SMTP-SSL due to deprecation
which prevented the (direct) dependency from being installed (via another
dependency), resulting in breaking function for encrypted/secured mail
destinations.

This change adds a direct dependency on IO::Socket::SSL as it ought to have
been originally.

[1] https://svnweb.freebsd.org/changeset/ports/431794

Reported by: ns5 (via IRC)
Approved by: portmgr (blanket: broken dependencies)
MFH: 2018Q3