Installing plugins from remote URL requires `git`

[karthik2804]

Installing plugins using a remote URL requires git. Reported by user on discord

$ spin plugin install -y --url https://github.com/fermyon/platform-plugin/releases/download/canary/platform.json
Error: failed to connect to endpoint https://github.com/fermyon/spin-plugins/: Error cloning Git repo https://github.com/fermyon/spin-plugi
ns/: `git` command not found - is git installed?

ref: https://discord.com/channels/926888690310053918/1170433556955271339/1170447199130353665