security update: httpoison

[kp-cat]

Describe the purpose of your pull request

• Security update

Related issues (only if applicable)

• https://trello.com/c/gmXc2WLf/2430-elixir-sdk?search_id=4f280d02-e91d-4e5d-9687-62ba91a9a37d

Security (only if applicable)

• mix.exs: bumped the httpoison constraint from ~> 1.7 or ~> 2.0 to ~> 2.0 or ~> 3.0.
• mix.lock: resolved to httpoison 3.0.0 (was 2.2.3), which pulls in hackney 4.4.3 (was 1.25.0). httpoison's changelog states 3.0.0 "upgrades to hackney 4.0, which fixes several CVEs
  (atom-table exhaustion via URL schemes, HTTP header injection, WebSocket buffer limits and more)" — this is almost certainly the high-severity vuln Snyk flagged.
• Also picked up minor bumps: certifi, idna, mimerl, parse_trans, plus new transitive deps h2, quic, webtransport (hackney 4.x's HTTP/2 and QUIC support).

Requirement checklist (only if applicable)

• I have covered the applied changes with automated tests.
• I have executed the full automated test set against my changes.
• I have validated my changes against all supported platform versions.
• I have read and accepted the contribution agreement.