Decommission snap on the parked/unmigrated CLIs (salesforce-cli, hubspot-cli)

[rianjs]

Follow-up to #36 (rollout step 12/12). #36's actionable items are done; this carries the remainder that is blocked on still-pending migrations, so the epic can close while the residual is tracked here.

Remaining snap decommission

• salesforce-cli — drop snap/snapcraft.yaml. Blocked by Conform CI/CD to repo/CI/CD standards salesforce-cli#45 (parked — no testability, same call as the INT-310 / output-rendering sfdc parking). Do it when sfdc un-parks and migrates.
• hubspot-cli — drop snap/snapcraft.yaml + the snap job in release.yml. Blocked by Conform CI/CD to repo/CI/CD standards hubspot-cli#54 (migration not yet done). Fold the snap removal into that migration.
• Orphaned snap-config sweep — Decommission deprecated distribution channels (snap/Formula) — tracking #36 noted ~3 orphaned snapcraft.yaml configs. Locally only salesforce-cli + hubspot-cli carry one; re-sweep across all collective repos once the two above migrate and confirm none remain (distribution.md §7).

Already done in #36

• snap removed from slack-chat-api, newrelic-cli, atlassian-cli, google-readonly (their migration PRs).
• homebrew-tap stale Formula + old-name casks removed (gro/gmail-ro → Remove decommissioned gro/gmail-ro casks and Formula homebrew-tap#16).
• linux-packages carries no snap remnants (verified).
• No migrated repo's .goreleaser has a brews: block, so Formula can't be regenerated; snap is gone from every release workflow.

Acceptance

• No release workflow in salesforce-cli / hubspot-cli can build a snap.
• No orphaned snapcraft.yaml remains in any collective repo.