Temporarily remove "Events" from logs README

[tigrannajaryan]

@jack-berg mentioned that https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/logs/README.md references Events.

We are planning on declaring Logs API/SDK stable and it would be useful to also declare README stable. Further additive changes to the README will be allowed. However because we are not declaring Events stable we can't declare the README stable as is.

I think we need to remove/move elsewhere bits about Events from README for now to allow marking the file as Stable. Once we arrive at stable definition for Events the relevant bits can be added to the README.