devel/gopls: update to 0.7.4
Changelog:
- Editing support for Go template files
- Improved support for generic code when using the Go 1.18 beta
- Various bug fixes
(https://github.com/golang/tools/releases/tag/gopls%2Fv0.7.4)
PR: 260469
Reported by: Robert Clausecker <fuz@fuz.su> (maintainer)