chore: delete release-plz GHA

[triarius]

It's not capable of running on forks.

[github-actions]

Package	Line Rate	Complexity	Health
src.backend	78%	0	✔
src	87%	0	✔
src.cli	83%	0	✔
src.cli.alias	89%	0	✔
src.cli.args	97%	0	✔
src.cli.backends	95%	0	✔
src.cli.cache	95%	0	✔
src.cli.config	92%	0	✔
src.cli.direnv	80%	0	✔
src.cli.generate	87%	0	✔
src.cli.plugins	86%	0	✔
src.cli.settings	93%	0	✔
src.cli.sync	29%	0	❌
src.cli.tasks	71%	0	➖
src.config.config_file	89%	0	✔
src.config	87%	0	✔
src.plugins	90%	0	✔
src.plugins.core	56%	0	➖
src.shell	98%	0	✔
src.toolset	86%	0	✔
src.ui	64%	0	➖
Summary	81% (13648 / 16755)	0	✔