[docs] Fix keyserver port numer, add instructions for connecting from physical device

Summary:
Issue: https://linear.app/comm/issue/ENG-2602/ip-port-in-dev-environmentmd

• Keyserver runs on port 9000, so I fixed that information.
• I called it "Expo lanucher screen" based on this expo doc: https://docs.expo.dev/development/use-development-builds/#the-launcher-screen
• I moved the instructions to find the IP address since now they are needed one section up
• I changed the instructions to find the IP address as discussed in the linear issue, because the GUI based ones were not working for macOS Ventura anymore. The terminal based ones are more universal.

Test Plan: Viewed rendered markdown

Reviewers: O6 Docs, ashoat, bartek

Reviewed By: O6 Docs, ashoat, bartek

Subscribers: bartek, ashoat, tomek, atul

Differential Revision: https://phab.comm.dev/D6249