install: fetch Arch package from packages.smallstep.com (EFF-173)#4

tashian merged 1 commit intomainsmallstep/step-agent-plugin:mainfrom

carl/eff-173-arch-agent-builds-are-not-pushed-to-gcssmallstep/step-agent-plugin:carl/eff-173-arch-agent-builds-are-not-pushed-to-gcsCopy head branch name to clipboard