Update Posthog Snippet

[ufkhan97]

Overview
We're reconfiguring how Posthog is set up to make it easier to track users across multiple subdomains (e.g if they go from explorer to builder or gitcoin.co to manager). This will let us get a much better picture of user flows/paths

Details
Replace the current posthog snippet with the new one (sharing in slack)

[linear]

PAR-417 Update Posthog Snippet