x11/nwg-drawer: update to 0.7.4

While here:

• update license of gotk4 to MPL-2.0
• switch to GO_MODULE
• update pkg-descr

Changelog:

• https://github.com/nwg-piotr/nwg-drawer/releases/tag/v0.6.4
• https://github.com/nwg-piotr/nwg-drawer/releases/tag/v0.6.5
• https://github.com/nwg-piotr/nwg-drawer/releases/tag/v0.7.0
• https://github.com/nwg-piotr/nwg-drawer/releases/tag/v0.7.1
• https://github.com/nwg-piotr/nwg-drawer/releases/tag/v0.7.2
• https://github.com/nwg-piotr/nwg-drawer/releases/tag/v0.7.3
• https://github.com/nwg-piotr/nwg-drawer/releases/tag/v0.7.4

Reported by: Repology