sysutils/elephant: update to 2.1.8

Changelog:

• https://github.com/abenz1267/elephant/releases/tag/v2.1.5
• https://github.com/abenz1267/elephant/releases/tag/v2.1.6
• https://github.com/abenz1267/elephant/releases/tag/v2.1.7
• https://github.com/abenz1267/elephant/releases/tag/v2.1.8

Reported by: GitHub (watch releases)