sensor-monitor: Fix missing function prototype

Add the missing ThresholdAlarmLogger::interfacesRemoved function
prototype.  This passed CI because the --enable-sensor-monitor flag
must not be turned on.

Signed-off-by: Matt Spinler <spinler@us.ibm.com>
Change-Id: I5ad5617bd56ae6649d6adde31faa02f9326d0483
1 file changed