math/cadabra2: Update from 2.1.4 to 2.1.5

[joneum]

Summary

• math/cadabra2: Update from 2.1.4 to 2.1.5

PR: 221306
Submitted by: Yuri Victorovich <[e-mail]> (maintainer)
Approved by: xxx (mentor)
#Differential Revision: https://reviews.freebsd.org/Dxxxxx

Test Plan

:~/dev/ports/math/cadabra2 % portlint -AC
WARN: Makefile: Consider adding support for a NLS knob to conditionally disable gettext support.
WARN: Makefile: for new port, make $FreeBSD$ tag in comment section empty, to make SVN happy.
0 fatal errors and 2 warnings found.

poudriere testport:

10.3-amd64
10.3-i386
11.1-amd64
11.1-i386
12.0-CURRENT r321899 amd64
12.0-CURRENT r321913 i386