Add missing return type for _scroll_marquee()

Author: tekktrik

adafruit_ht16k33/segments.py

@@ -365,7 +365,7 @@ def marquee(self, text: str, delay: float = 0.25, loop: bool = True) -> None:
             else:
                 self._scroll_marquee(text, delay)
 
-    def _scroll_marquee(self, text: str, delay: float):
+    def _scroll_marquee(self, text: str, delay: float) -> None:
         """Scroll through the text string once using the delay"""
         char_is_dot = False
         for character in text: