faces/pulsometer: remember pulsometer calibration

Avoid resetting it to default when the face is activated.
Set the default pulsometer calibration once,
only when the face is first set up.

This makes it remember the calibration set by the user.
It will no longer overwrite it.

movement/watch_faces/complication/pulsometer_face.c

@@ -138,7 +138,9 @@ void pulsometer_face_setup(movement_settings_t *settings, uint8_t watch_face_ind
     (void) watch_face_index;
 
     if (*context_ptr == NULL) {
-        *context_ptr = malloc(sizeof(pulsometer_state_t));
+        pulsometer_state_t *pulsometer = malloc(sizeof(pulsometer_state_t));
+        pulsometer->calibration = PULSOMETER_FACE_CALIBRATION_DEFAULT;
+        *context_ptr = pulsometer;
     }
 }
 
@@ -147,7 +149,6 @@ void pulsometer_face_activate(movement_settings_t *settings, void *context) {
 
     pulsometer_state_t *pulsometer = context;
 
-    pulsometer->calibration = PULSOMETER_FACE_CALIBRATION_DEFAULT;
     pulsometer->measuring = false;
     pulsometer->pulses = 0;
     pulsometer->ticks = 0;