Remove extra and context from Frontend Internal event's code and documentation

Problem

Currently, Internal events in frontend supports extra and context attribute, but backend does not. So remove it from the code and the documentation until we decide on the approach we want to support it.

Migrate the events that are using those to standard snowplow tracking. This one I could find to migrate.

Update props section in the quickstart guide to point to standard snowplow documentation for those who want to use extra and context attibutes.

Reference - https://gitlab.slack.com/archives/CL3A7GFPF/p1699429030990379

Desired Outcome

extra and context should be removed from the code and documentation.

Potential Solution

Remove it from the code and update documentation.

How to verify

Verify the documentation does not mention extra and context for internal events and code has been removed.