Outdated getting started docs

[yhabteab]

Hi, while going through the getting started docs I noticed that the example code listed there for how to register a custom global log handler is outdated and does not compile anymore. Specifically the SetLogHandler signature seems to have changed to use nostd::shared_ptr instead of non-pointer value. Here's the offending line:

opentelemetry::sdk::common::internal_log::GlobalLogHandler::SetLogHandler(CustomLogHandler());

_{Tip: React with 👍 to help prioritize this issue. Please use comments to provide useful context, avoiding +1 or me too, to help us triage it. Learn more here.}