Replaced arbitrary sleep with a wait until response on all functions

gqrxHandler.py

@@ -26,12 +26,12 @@ class GQRXHandler():
             squelch = float(-abs(squelch))
         print(f"Changing squelch to {squelch}")
         self.tel_conn.write(bytes(f"L SQL {float(squelch)}", 'utf-8'))
-        sleep(.5)
+        self.tel_conn.read_until(b'RPRT 0')
 
     def change_mode(self, mode):
         print(f"Changing mode to {mode}")
         self.tel_conn.write(bytes(f"M {str(mode)}", 'utf-8'))
-        sleep(.5)
+        self.tel_conn.read_until(b'RPRT 0')
 
     def set_all_settings(self, mode, squelch, freq):
         self.change_squelch(0)