regulators: Remove monitoring freq from comments

Update doxygen comments to remove the exact frequency of sensor
monitoring and phase fault detection.

Currently sensors are monitored every second and phase faults are
detected every 15 seconds.  However, that could change in the future.

Signed-off-by: Shawn McCarney <shawnmm@us.ibm.com>
Change-Id: I3ac39955721fde98dfe9e6059693ceeea7e504c2
diff --git a/phosphor-regulators/src/system.hpp b/phosphor-regulators/src/system.hpp
index caa3804..accd7f0 100644
--- a/phosphor-regulators/src/system.hpp
+++ b/phosphor-regulators/src/system.hpp
@@ -95,7 +95,7 @@
     /**
      * Detect redundant phase faults in regulator devices in the system.
      *
-     * This method should be called every 15 seconds.
+     * This method should be called repeatedly based on a timer.
      *
      * @param services system services like error logging and the journal
      */
@@ -138,7 +138,7 @@
      * Monitors the sensors for the voltage rails produced by this system, if
      * any.
      *
-     * This method should be called once per second.
+     * This method should be called repeatedly based on a timer.
      *
      * @param services system services like error logging and the journal
      */