- Remove reference to default events from the overall workload
documentation. It was, as of recently, outdated, and was also
redundant, as the actual defaults will be in the parameter-specific
documentation.
- Remove reference to Android-specific trace-cmd binary -- this was not
true for a long time.
- Clarify that the on-host trace-cmd binary is now optional due to the
report_on_target config.
- Fix a few misc typos.