Adapting to W0707 pylint message

W0707: Consider explicitly re-raising using the 'from' keyword (raise-missing-from):
> 2020-08-23T08:28:02.9225541Z ************* Module adafruit_pm25.i2c
> 2020-08-23T08:28:02.9226318Z adafruit_pm25/i2c.py:84:16: W0707: Consider explicitly re-raising using the 'from' keyword (raise-missing-from)

Author: dglaude

adafruit_pm25/i2c.py

@@ -80,5 +80,5 @@ def _read_into_buffer(self):
         with self.i2c_device as i2c:
             try:
                 i2c.readinto(self._buffer)
-            except OSError:
-                raise RuntimeError("Unable to read from PM2.5 over I2C")
+            except OSError as err:
+                raise RuntimeError("Unable to read from PM2.5 over I2C") from err