[RTTY] Fixed typos in examples

examples/RTTY/RTTY_Transmit/RTTY_Transmit.ino

@@ -72,7 +72,7 @@ void setup() {
     // All transmissions in loop() (strings and numbers)
     // will now be encoded using ITA2 code
 
-    // ASCII characters that do not have ITA2 euqivalent
+    // ASCII characters that do not have ITA2 equivalent
     // will be sent as NUL (including lower case letters!)
   */
 }