ci(upload-charm): use charmcraft from latest/candidate #307

Job	Run time
Publish Charm / Generate the Charm Matrix	3s
Publish Charm / Generate the Charm Matrix	3s
Run Tests / Integration Tests	25m 9s
Run Tests / Integration Tests	25m 45s
Run Tests / Lint Check	16s
Run Tests / Lint Check	16s
Run Tests / Unit Test	26s
Run Tests / Unit Test	26s
Run Tests / Check libraries / Check libraries	29s
Run Tests / Check libraries / Check libraries	29s
Run Tests / Check libraries / Lint	10s
Run Tests / Check libraries / Lint	10s
Publish Charm / Publish Charm (./)	11m 8s
Publish Charm / Publish Charm (./)	11m 8s
	1h 15m 58s

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