Update docs for simple usage of scripts/build_apple_frameworks.sh (#11174)

### Summary
After #11115, we don't need to
pass all the flags.

### Test plan

```
rg "build_apple_frameworks" -t markdown
```

Author: jathu

docs/source/using-executorch-ios.md

@@ -135,7 +135,7 @@ sudo /Applications/CMake.app/Contents/bin/cmake-gui --install
 For example, the following command will build the ExecuTorch Runtime along with all available kernels and backends for the Apple platform in both Release and Debug modes:
 
 ```bash
-./scripts/build_apple_frameworks.sh --Release --Debug --coreml --mps --xnnpack --custom --optimized --portable --quantized
+./scripts/build_apple_frameworks.sh
 ```
 
 After the build finishes successfully, the resulting frameworks can be found in the `cmake-out` directory.

examples/demo-apps/apple_ios/LLaMA/docs/delegates/xnnpack_README.md

@@ -138,7 +138,7 @@ curl -LO "https://github.com/facebook/buck2/releases/download/${BUCK2_RELEASE_DA
 zstd -cdq "$BUCK2_ARCHIVE" > "$BUCK2" && chmod +x "$BUCK2"
 rm "$BUCK2_ARCHIVE"
 
-./scripts/build_apple_frameworks.sh --buck2="$(realpath $BUCK2)" --coreml --custom --mps --optimized --portable --quantized --xnnpack
+./scripts/build_apple_frameworks.sh
 ```
 
  After the build finishes successfully, the resulting frameworks can be found in the `cmake-out` directory. Copy them to your project and link them against your targets.