ci: update juju to 3.1 and microk8s to 1.25 #332

Job	Run time
Publish Charm / Generate the Charm Matrix	5s
Run Tests / Lint	19s
Run Tests / Integration tests (microk8s) (katib-controller)	17m 1s
Run Tests / Test the bundle	6h 0m 17s
Run Tests / Unit tests (katib-db-manager)	18s
Run Tests / Check libraries (katib-controller) / Check libraries	27s
Run Tests / Check libraries (katib-controller) / Lint	16s
Run Tests / Check libraries (katib-db-manager) / Check libraries	1m 38s
Run Tests / Check libraries (katib-db-manager) / Lint	11s
Run Tests / Check libraries (katib-ui) / Check libraries	26s
Run Tests / Check libraries (katib-ui) / Lint	11s
Publish Charm / Publish Charm (./charms/katib-ui)	33m 17s
Publish Charm / Publish Charm (./charms/katib-db-manager)	35m 32s
Publish Charm / Publish Charm (./charms/katib-controller)	3m 24s
	7h 33m 22s

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