Apply suggestion from @Copilot

Co-authored-by: Copilot <[email protected]>

Author: clydebarrow

components/mapping.rst

@@ -92,7 +92,7 @@ A more complex example follows:
       - platform: ...
         # update the display drawing random text in random colors
         lambda: |-
-          auto color = color_map.get(random_uint32() % 3]); # Uses get() to index the color_map
+          auto color = color_map.get(random_uint32() % 4]); # Uses get() to index the color_map
           it.printf(100, 100, id(roboto20), color, id(string_map)[random_uint32() % 3].c_str(), Color(0));