start/exceptions "A complete example" uses incorrect type for semihosted stdout stream

[matej-almasi]

In Exceptions sub-chapter of Getting Started, the complete example uses incorrect type for the semihosted stdout stream.

The example uses use hio::HStdout instead of hio::HostStream which should be used when using cortex-m-semihosting = "0.5" per manifest included in the cortex-m-quickstart template.