typo fix

Author: ladyada

wled00/pin_manager.cpp

@@ -217,7 +217,7 @@ bool PinManager::isPinOk(byte gpio, bool output)
 
     if (strncmp_P(PSTR("ESP32-U4WDH"), ESP.getChipModel(), 11) == 0) {
       // this chip has 4 MB of internal Flash and different packaging, so available pins are different!
-      if ((gpio == 1) || (gpio == 3) || ((gpio >= 6) && (gpio =< 8)) ||
+      if ((gpio == 1) || (gpio == 3) || ((gpio >= 6) && (gpio <= 8)) ||
           (gpio == 11) || (gpio == 16) || (gpio == 17) || (gpio == 20) || 
           (gpio == 24) || ((gpio >= 28) && (gpio <= 31)))
         return false;