fix(spo2): Use time, not utime

preload/apps/spo2/__init__.py

 import max86150
 import display
-import utime
+import time
 import buttons
 import spo2_algo
-import utime
 import color
 
 
@@ -29,7 +28,7 @@ class SPO2:
         self.average = 0
         self.prev_w_ir = 0
         self.prev_w_red = 0
-        self.t0 = utime.time_ms()
+        self.t0 = time.time_ms()
 
     def open(self):
         def callback(datasets):
@@ -46,8 +45,8 @@ class SPO2:
                     self.ir_history, self.red_history
                 )
 
-                print(utime.time_ms() - self.t0, spo2, spo2_valid, hr, hr_valid)
-                self.t0 = utime.time_ms()
+                print(time.time_ms() - self.t0, spo2, spo2_valid, hr, hr_valid)
+                self.t0 = time.time_ms()
                 if hr_valid:
                     self.disp.print("HR: {0:3} bpm".format(hr), posy=20)
                 else:
@@ -162,7 +161,7 @@ if __name__ == "__main__":
         raise e
 
     while True:
-        utime.sleep(0.1)
+        time.sleep(0.1)
         if buttons.read(buttons.BOTTOM_RIGHT):
             pass
         while buttons.read(buttons.BOTTOM_RIGHT):