AP_NavEKF3: use standard unit descriptor for milliseconds

libraries/AP_NavEKF3/AP_NavEKF3.cpp

@@ -219,7 +219,7 @@ const AP_Param::GroupInfo NavEKF3::var_info[] = {
     // @Increment: 10
     // @RebootRequired: True
     // @User: Advanced
-    // @Units: msec
+    // @Units: milliseconds
     AP_GROUPINFO("HGT_DELAY", 12, NavEKF3, _hgtDelay_ms, 60),
 
     // Magnetometer measurement parameters
@@ -321,7 +321,7 @@ const AP_Param::GroupInfo NavEKF3::var_info[] = {
     // @Increment: 10
     // @RebootRequired: True
     // @User: Advanced
-    // @Units: msec
+    // @Units: milliseconds
     AP_GROUPINFO("FLOW_DELAY", 23, NavEKF3, _flowDelay_ms, FLOW_MEAS_DELAY),
 
     // State and Covariance Predition Parameters
@@ -503,7 +503,7 @@ const AP_Param::GroupInfo NavEKF3::var_info[] = {
     // @Increment: 10
     // @RebootRequired: True
     // @User: Advanced
-    // @Units: msec
+    // @Units: milliseconds
     AP_GROUPINFO("BCN_DELAY", 46, NavEKF3, _rngBcnDelay_ms, 50),
 
     // @Param: RNG_USE_SPD