docs: drop --clean from the Expo React header build fix

[eandreeva-twr]

Drops --clean from the expo prebuild command in the iOS build fails with 'React/RCTBridge.h' file not found troubleshooting entry of the Expo installation guide.

Updating expo-modules-autolinking and re-running prebuild is enough to pick up the fixed autolinking; wiping the native directories isn't needed, and --clean costs the reader a full rebuild from scratch.

The lead-in sentence ("regenerate the native project") is accurate for a plain prebuild, so no prose change was needed.

Deliberately unchanged

The other two expo prebuild --clean calls in the same article are left as they are — this change is scoped to the one troubleshooting entry:

• the SPM setup step under Adapty SDK 4.0: enable Swift Package Manager
• the Minimum iOS version error troubleshooting entry

Verification

• node scripts/check-mdx-parse.mjs — 5929 files parsed cleanly
• node scripts/lint-mdx.mjs on the edited file — OK