x11-fonts/iosevka: Update to 2.3.0

Changelog for 2.3.0:

• Experimental proportional variant Aile!
• Experimental proportional variant Etoile!
• Experimental wide variant Expanded!
• Adjusted horizontal stroke width for heavy weights.

https://github.com/be5invis/Iosevka/releases/tag/v2.3.0

• Add a new option called EXPERIMENTAL for experimental font variants.
• Mute some insignificant commands in do-install.
• Add a maintainer target to ease the regeneration of pkg-plist.

Reported by: Repology