last easy-to-fix warning

Author: ladyada

M4_Eyes/M4_Eyes.ino

@@ -163,7 +163,7 @@ void setup() {
   // config1.eye, config2.eye or config3.eye instead). Keep fingers clear
   // of the nose booper when doing this...it self-calibrates on startup.
   // DO THIS BEFORE THE SPLASH SO IT DOESN'T REQUIRE A LENGTHY HOLD.
-  char *filename = "config.eye";
+  char *filename = (char *)"config.eye";
 
   uint32_t buttonState = arcada.readButtons();
   if((buttonState & ARCADA_BUTTONMASK_UP) && arcada.exists("config1.eye")) {