ci: add permissions for releasing server rock (#1720) #2

Job	Run time
dashboard-tests / Test JIMM with the Juju dashboard	28m 20s
release-server-rock / publish	7m 47s
release-binaries / goreleaser	11m 1s
release-snaps / build-jimm-server	11m 4s
release-snaps / build-and-release-jaas-plugin / build	7m 56s
release-snaps / build-and-release-jaas-plugin / publish	2m 58s
	1h 9m 6s

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