connecting.md: mention PICODATA_ADMIN_PASSWORD

Summary

• connecting.md: mention PICODATA_ADMIN_PASSWORD

Address changes from picodata@ddcc5664

picodata 24.5.0-233-gddcc5664

---

• Close #315 (closed)
• Follow-up for picodata!1164 (merged)
• Cherry-pick to: 24.5
• Staging: https://docs.binary.picodata.io/picodata/asabirov_update_connecting_md/tutorial/connecting/#set_admin_password