Fix trivial extra "\n" on web update success (#6350)

Fixes #3290

Author: earlephilhower

libraries/ESP8266HTTPUpdateServer/src/ESP8266HTTPUpdateServer-impl.h

@@ -16,7 +16,7 @@ static const char serverIndex[] PROGMEM =
                </form>
          </body></html>)";
 static const char successResponse[] PROGMEM = 
-  "<META http-equiv=\"refresh\" content=\"15;URL=/\">Update Success! Rebooting...\n";
+  "<META http-equiv=\"refresh\" content=\"15;URL=/\">Update Success! Rebooting...";
 
 template <typename ServerType>
 ESP8266HTTPUpdateServerTemplate<ServerType>::ESP8266HTTPUpdateServerTemplate(bool serial_debug)