Fix non-ascii character.

Author: ogatatsu

boards.txt

@@ -477,7 +477,7 @@ particle_xenon.menu.debug.l3=Level 3 (Segger SystemView)
 particle_xenon.menu.debug.l3.build.debug_flags=-DCFG_DEBUG=3
 
 # ----------------------------------
-# Raytac MDBT50Q – RX
+# Raytac MDBT50Q - RX
 # ----------------------------------
 mdbt50qrx.name=Raytac MDBT50Q-RX Dongle