[docs] Step: fix possible overflow on mobile in certain cases

[Simek]

Why

Fixes ENG-9002

How

Make sure that Step component do not exceed the viewport on mobile, when it contains a flex base component in its content.

Test Plan

The changes have been tested by running docs app locally.

Preview

[linear]

ENG-9002 Terminal snippets in Step component cause docs text to overflow on phones

See https://docs.expo.dev/build/internal-distribution/#configure-app-signing. Use Chrome dev tools to simulate a phone (I tried iPhone 12 Pro). The text gets cut off: https://twitter.com/charlienoller_/status/1670848489171845125

The cause looks to be the terminal UI snippet that's a bit later in the section. You can verify this by changing white-space: pre to white-space: normal on the elements and the text no longer overflows. I don't think this is the fix — just confirms the terminal snippet is the cause of the overflow.