Update steps to switch logging to InnoDB

The current documentation is confusing and out of date. I've just switched a site to use InnoDB for logging and it took me a while to work out what to do. Once I had worked it out, it was pretty simple so to avoid others having the same issue, I've updated the documentation.

The documentation was updated in 64938bf7 following the core changes in https://github.com/civicrm/civicrm-core/pull/14256

However the section on 'Swapping over to INNODB for storage format' wasn't updated and is now out of date. There is no longer any need to install a separate extension. All you need to do is run the core API call:

cv api System.updatelogtables forceEngineMigration=1

I'll submit an MR to fix this.