I noticed this first via the Config API which shows a config element called "commitIntervalLowerBound" under the updateHandler section. A quick search of this property shows it that it is not used anywhere. In fact, some of the old solrconfig.xml used by tests and the extraction contrib had the following to say about this property:
<!-- represents a lower bound on the frequency that commits may occur (in seconds). NOTE: not yet implemented <commitIntervalLowerBound>0</commitIntervalLowerBound> -->
This is clearly not used so let's remove it.