Update adafruit_tlv493d.py

Fixed units in docstring. Alternatively, multiple the returned values  by 1000 in `_unpack_and_scale` to report microteslas (what all the other magnetic sensors from adafruit report)

Author: BrianPugh

adafruit_tlv493d.py

@@ -158,7 +158,7 @@ def _set_write_key(self, key: str, value: int) -> None:
     @property
     def magnetic(self) -> Tuple[float, float, float]:
         """The processed magnetometer sensor values.
-        A 3-tuple of X, Y, Z axis values in microteslas that are signed floats.
+        A 3-tuple of X, Y, Z axis values in milliteslas that are signed floats.
         """
         self._read_i2c()  # update read registers
         x_top = self._get_read_key("BX1")