chore(deps): update mattermost support dependencies #849

Job	Run time
validate (install, registry1) / run	1s
validate (install, unicorn) / run	1s
validate (install, upstream) / run	3s
validate (upgrade, registry1) / run	1s
validate (upgrade, unicorn) / run	1s
validate (upgrade, upstream) / run	1s
	8s

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