Fix incorrect class name in SimpleTextDisplay documentation

Author: terop

adafruit_simple_text_display.py

@@ -104,7 +104,7 @@ def __init__(  # pylint: disable=too-many-arguments
                        the colors built into the library. For example, if you import the library
                        as ``from adafruit_simple_text_display import SimpleTextDisplay``, you can
                        indicate the colors as follows:
-                       ``colors=(SimpleDisplayText.WHITE, SimpleDisplayText.RED)``.
+                       ``colors=(SimpleTextDisplay.WHITE, SimpleTextDisplay.RED)``.
         :param display: The display object. Defaults to assuming a built-in display. To use with an
                         external display, instantiate the display object and provide it here.
                         Defaults to ``board.DISPLAY``.