Clarify 10hz logging rate instead of 100 mhz

examples/shield_sdlog/shield_sdlog.ino

@@ -124,7 +124,7 @@ void setup() {
   // For logging data, we don't suggest using anything but either RMC only or RMC+GGA
   // to keep the log files at a reasonable size
   // Set the update rate
-  GPS.sendCommand(PMTK_SET_NMEA_UPDATE_1HZ);   // 100mHz,1Hz or 5Hz update rate
+  GPS.sendCommand(PMTK_SET_NMEA_UPDATE_1HZ);   // 10Hz, 1Hz or 5Hz update rate
 
   // Turn off updates on antenna status, if the firmware permits it
   GPS.sendCommand(PGCMD_NOANTENNA);