api/parameters/Color: remove BROWN

Brown has the same hue as orange, just with a lower value and/or
saturation,  so it does not need to have a separate Color instance.
It is also not supported by the color_map methods.

It was originally included in this list because the EV3 Color Sensor
can technically detect it. This is not reliable, however, as it is
also reports this value for orange objects at a slightly larger
distance. The implementation may be updated to return orange
in both cases. If the original values are required, the LUMPDevice
may be used to get the original color index.

pybricks/parameters.py

@@ -36,7 +36,6 @@ class Color(_PybricksEnum):
     .. data:: YELLOW
     .. data:: RED
     .. data:: WHITE
-    .. data:: BROWN
     .. data:: ORANGE
     .. data:: VIOLET
     """
@@ -47,7 +46,6 @@ class Color(_PybricksEnum):
     YELLOW = 4
     RED = 5
     WHITE = 6
-    BROWN = 7
     ORANGE = 8
     VIOLET = 9