fixing rssi typo

Author: siddacious

adafruit_esp32spi/adafruit_esp32spi_wifimanager.py

@@ -346,4 +346,4 @@ def signal_strength(self):
         """
         if not self.esp.is_connected:
             self.connect()
-        return self.esp.rssi()
+        return self.esp.rssi