Fix: parse is_enterprise_install string

[yunginnanet]

Cause: (*fmt.wrapError)(0xc004b8f3c0)(parsing slash command: json: cannot unmarshal string into Go struct field SlashCommand.is_enterprise_install of type bool),

sometimes we get "is_enterprise_install":"false", sometimes we get "is_enterprise_install": false

add ,string: and now both work

[yunginnanet]

errr, actually it won't be that simple

i'll look at this later - needs an issue - can't do it rn