deps: Drop expo-cli, the legacy Expo CLI

We don't use the `expo` CLI in normal development; only when
upgrading Expo itself.  Discussion:
  #5602 (comment)

This `expo-cli` package is apparently in maintenance mode.
It doesn't and won't support Node 18, the current LTS:
  expo/expo-cli#4583
  expo/expo-cli#4281

That effectively gives it an EOL of 2023-09, the EOL date of Node 16,
which is less than a year away.  It also means an error when just
trying to run `yarn install` with a newer Node version.  So it'd be
good to get it out of our dependencies.

There's a successor CLI now:
  https://blog.expo.dev/the-new-expo-cli-f4250d8e3421
That one is shipped with Expo itself, starting with Expo 46.
We're on Expo 45 at the moment, so we still have one more upgrade
before then; when we go to do that upgrade, we might need some
ad-hocery to get the CLI (either the old one or the new one,
which IIUC was in beta in the Expo 45 period.)  Until then,
just drop it.

As a bonus, dropping this sheds about 90MB from our node_modules tree.
(At least for now; maybe Expo 46 will bring that all back.)

package.json

@@ -105,7 +105,6 @@
     "eslint-plugin-prettier": "^4.0.0",
     "eslint-plugin-react": "^7.24.0",
     "eslint-plugin-react-hooks": "^4.5.0",
-    "expo-cli": "^6.0.5",
     "flow-bin": "^0.170.0",
     "flow-coverage-report": "^0.8.0",
     "flow-typed": "^3.3.1",